Dressing well shouldn't be simply a matter of weight, and it shouldn't simply be a matter of age either. We're all aware that a 40 or 50-year old can't dress like a teenager - that's just plain sad. But once you hit 30, I reckon, you can start developing a personal style that can take you, with annual updates, through the rest of your life.

So what should it be based on? Here are some handy 'rules' - rules in the sense of 'for the obedience of fools and the guidance of wise women'...

1 Dress like a grown-up

You are not a little girl any more, so knock off the ruffles and bows and all the cutesy, ditsy stuff. Shorty ra-ra skirts, itsy-bitsy little tops, girly prints, t-shirts with bunnies on or 'sexy' sayings. These are no longer for you. Instead, look for reserved, adult clothing with some structure and shape to it. Long sleeves on tops, long legs on trousers, whatever necklines are most flattering for you personally, clothing without bells and whistles, classic block colours - black, white, navy, cream and good neutrals. Build your wardrobe around these items and then add your own twist and flair.

2 Keep it covered

I don't mean nun-like, but in general, follow the 30 per cent rule - only show 30 per cent of your body at any one time, even for evening. Now is the time to look like a woman who's actually getting sex, rather than desperately looking for it. If you've got great arms, by all means wear a sleeveless top, but keep the neck high for maximum impact and cover your legs. If you're wearing backless, keep the front high: if you're wearing a plunge front, keep the back high... The fact is: if you reveal your flesh, you are going to be compared with every 20-year-old who does the same - it is far better to leave people guessing about how gorgeous you are than to show them you're not.

3 Keep it simple

There's a good reason I've banged on endlessly in this blog about 'classic clothes', and that's because they work. And one key thing that differentiates classic clothes is that they have simple lines - their design is pared down to the essentials. Whatever you're wearing, seek simplicity and avoid exaggeration. Don't wear things with 25 colours and added bits of gewgaws all over them - contrasting appliques and heavy beading in clashing colours. Avoid big shoulders, poofy skirts, huge floppy collars and lapels, and weird sleeve designs. These don't do anyone any favours - even teenagers, but teenagers have a right to look stupid if they want to. Grown up girls need to raise the bar a little - aiming for elegance and class. Keeping it simple works with any type of clothing - blouses with small collars, t-shirts with scoop or v necks, blouses with clean French cuffs, pencil skirts, clean-lined jackets with vertical seaming....

4 Keep it clean

When I say clean, I do mean physically clean. Being scruffy is the prerogative of the young, the rich and the mad, but the rest of us have to conform a little even if we may not like it. Going out with chipped nail polish, undyed roots, a moustache or clothes covered in dog hair just screams middle-aged rut, and don't think that people won't notice because they will. Grown-up girls have to look groomed. Not polished necessarily, but soignée, as the French say - cared-for, put-together. A clean, crisp, groomed appearance always works, no matter what your lifestyle.

Yes, it takes a little application, but the effort repays itself a hundred-fold. Choose a haircut that you can maintain easily (or pay to have maintained). Keep your clothes clean (if you can't afford or don't wish to undertake dry cleaning, buy clothes you can wash at home). Do running repairs once a month - sewing buttons back on and taking your shoes for re-heeling. Iron things properly and treat stains before they set. Overall, treat your clothing as if it cost ten times the price.

5 Keep it quality

Quality wears better than rubbish, and whatever the item, quality cloth, cut and finish will show. Buy quality items wherever you can, even for basics - pima cotton t-shirts, Egyptian cotton blouses, cashmere and merino knitwear in plain colours, decent wool-rich suiting (a little stretch here can work wonders), a fantastic pair of jeans with the outside seam brought slightly forward to slim your thighs, and correct pocket placement. Watch out for the sales and stock up on basics from good manufacturers. It is better to have a smaller wardrobe of quality items than a large wardrobe of tat - the age of 40 is a good signal to upgrade your choice of fabric and cut.

When I say quality, this is quality at every level, so if you're strapped for cash, go for the best of a type. Rather than buying low-end fakes of high-end items, look for high-end democratic items at a lower price level. Instead of tinny gold-plate jewellery, buy handmade wooden beads; instead of a plastic leather-look handbag, buy a good-quality canvas bag; if you can't afford cashmere, buy merino on sale rather than a cheap acrylic sweater. In the long run, it will pay dividends.

I was astounded to see an old friend on Jess Carter Morley's latest video, on what to wear on Christmas Day.

I refer, sadly, not to a person, but to the sheep jumper by Chloe, which Carter-Morley, being too young to have worn one the first time round, simply thinks is cute and fun, mixed in among the red chiffons and winter-white silks that she imagines will give a lot more mileage (love, I haven't worn chiffon in over a decade...). 

Should I be wishing that I hadn't given my sheep jumper, so redolent of Princess Di, to my friend N for mucking out her horses?

I once had a big fetish for the picture jumpers that were so popular back in the 80s. I can't remember how many I had, but I certainly had a red one with white sheep, a navy one with white sheep, a navy one with pink pigs (and a built-in squeaker!), a sky-blue one with scottie dogs, not to mention the numerous landscape/umbrellas/intarsia/geometric multi-coloured sweaters I bought, wore and gave away (usually to N) over the course of a decade or so.

I could seriously wish some of them back again now, with our heating only on for four hours a day. I gave them away at a time when fashion seemed more important than warmth - I never envisaged a time when oil would be so expensive, and warmth so very very necessary. Not that I don't have enough clothes, you understand. Just that it would be nice to ring the changes a bit more often. 

As I type, I'm wearing my usual winter garb of undies, silk thermals, cashmere crewneck, cashmere poloneck, aran cardigan and a thick pair of wool ski trousers from Adrienne Vittadini. Oh, and of course a hat, Uggs, thermal knee-length socks and fingerless gloves.

Luckily, it is not as cold as last year, and I have worked out my routines much better. Our bedroom temperature is about 5 degrees - the same, as I snippily pointed out to my husband - as the fridge. But if I go to bed in a poloneck cashmere sweater, flannel pjs and a balaclava then I can sleep very well indeed - the key is to keep your head warm. Once in the bed, we have heated pads, an electric blanket, several blankets and 32 togs of goosedown duvet, perhaps one reason why the bed, all day and all night, remains a cat magnet, and getting out of bed each morning seems simple purgatory.

However, it is this time of day that is perhaps the worst - four in the afternoon. The heating comes on at 7.00am and the house is warm when we get up, but it clicks on and off until 2.00 and I don't light the woodburner till 5.00, after which I will be glued to its 22kw like Linus to his blanket. 

Oh well, enough whingeing. At least I HAVE central heating, which no-one else here does. Around this neck of the woods, the winter days generally begin by donning a thick dressing gown, slipping downstairs into a glacial kitchen and coaxing the woodburner back to life.

Which is what I myself am about to do.  

A reader, Susan, asked the other day, how should she care for cashmere?

"The sweaters I've gotten my family (second hand) seem to develop holes at an alarming rate. We gentle wash and flat dry them. Is this a good way to care for them? Also, is there a way to judge what quality of cashmere is in a sweater?"

Well, ouch, is my first reply. If these sweaters are developing holes, it usually means moth damage - at some point, possibly long before they got to you, they've been stored incorrectly and the moths have gotten in. You often don't notice this at first - it's only when the garment's washed that the damage becomes apparent. 

The good news is that the moths are easily killed by washing, and also by putting the garment in the freezer.  Whenever you buy a second-hand garment, popping it into the freezer for 24 hours is a good first port of call. 

Repair

Once you've got moth damage, how you repair it depends on how big the holes are. Most can be repaired easily by good old-fashioned darning, though it can be hard somtimes to get a colour match with the yarn. I will shortly be in this situation with a salmon-pink sweater that's developed some cat-claw holes - I just can't find a yarn to match the colour, so any repair is going to be more obvious than I would like. 

Bigger holes, usually caused by wear, can occur at the elbows or underarms. Under the arm, where the fabric can become thin, it can pay to back the inside of the underarm area with cloth, like a dress shield (only less stiff) or iron-on interfacing to strengthen the fabric. Holes at the elbows, in traditional British fashion, are treated by sewing on leather patches: preserving a good sweater in this obvious way is considered a subtle sign of quality, not thrift - a kind of quiet snobbery.

Wear at the wrists is best treated by sewing on bias binding to cover the crumbling edge of the garment. I make my own from stretch velvet, as I find this the most comfortable and compatible fabric, but you can buy bias binding if you prefer, though I find the commercial types rather stiff. I usually choose something contrasting rather than toning, and make a feature out of it. Satin also works well.

When a sweater is really completely done in, I quite often cut the sleeves off and make a waistcoat plus handwarmers/anklewarmers out of the remnants. 

Care

Susan says she gentle washes her sweaters and flat dries them, and that is indeed the best way to care for them. I am not, personally, precious about my cashmere - it all goes in the washing machine on 'wool wash' and cold (I pretty much wash ALL my clothes on cold unless they're filthy), and is then flat-dried on a rack. If you have the time and energy, a light press doesn't do any harm either, and it will go a lot easier if you refrigerate the garment first for 30 minutes or so. If you're washing only one or two sweaters at a time, put them in a lingerie bag so they don't get twisted and strained in the wash.

Storage

Always store your sweaters-in-use flat, and no more than three deep for preference, in order to maintain the 'loft' and not squash the fibres. If you wear them often, you needn't bother with drawer fresheners etc, but for anything in storage out of season you absolutely need moth repellent. Moths seem to prefer wool to all other fibres, and cashmere to all other wools, in my experience, so make sure you've got cedar balls or lavender bags or scented drawer paper or something in there.

The scent isn't to kill the moths - it's just to deter them, so anything strongly scented will do. Make sure that the drawer paper is the real deal and acid-free or the sweaters will discolour, though underneath the liner that actually touches your garments, plain old newspaper works very well as a repellent because moths hate the smell of the ink. 

Never, EVER put away a sweater dirty - ALWAYS wash it first. Even a single wear will soak the fibres in skin oils, dead skin etc, which are an absolute banquet to moths - they will beeline straight in on the soiled sweater and then happily munch their way through anything clean as well. They also love things like food drips down the front, or crumbs. Being clean and tidy here will pay dividends in the long run. 

Keep your drawers or shelves clean - make sure they're dusted and polished (repainting once a year can be a good idea too), and when you put your sweaters away at the end of winter, store them out of the light and absolutely smothered in lavender bags. Out of season I keep mine in 1930s suitcases with fabric linings and I spray perfume on tissues tucked into those linings. Perfumes like lemon and lavender seem to work very well, or some women swear by vanilla essence.

Let your spiders live - they eat moths. Better a few cobwebs than a munched sweater. And for when all else fails, keep a can of Doom handy. It's nasty stuff, but it really does work when you actually need to kill moths rather than just deter them.

Quality

A good quality cashmere sweater should feel luxuriously soft, heavy and thick, and in this regard, I've found two reliable indicators - age and the label. Sweaters from the 1950s and before can be found in three-ply cashmere, which is really no longer available. It feels thick and sturdy in your hands, and amazingly soft - it's also surprisingly heavy when you pick it up. Snap these up if you can.

Good modern cashmeres are usually two-ply (or 'double') - if a sweater is suspiciously cheap, it's probably one-ply, in which case it's simply selling the word 'cashmere' rather than the real concept. Most manufacturers are proud of their garments and will liberally sprinkle the knit with labels telling you the fabric quality. Many modern good-quality cashmeres come from Italy.

Cashmere varies widely in price because the original yarn varies widely in quality. Good yarn should be 16.8 microns thick or below, and comes from a very specific altitude. For the ordinary consumer, however, the best indicator is the price - a good quality new sweater should cost £200 or so, full price, excluding sale or damage. Cashmere-mix sweaters do not generally contain the best-quality cashmere either - manufacturers don't waste good cashmere by mixing it with lambswool or angora. 

Design also tells you a couple of things. A sweater should be fully-fashioned, with proper knitted-in sleeves, and should have long cuffs that you can fold back. 

Good labels have also never let me down. Although I have sweaters from Scotch House, Marks and Spencer, Jaegar etc, by far the best I own remain those from the traditional Scottish brands such as Pringle, Braemar and Ballantyne (traditionally, the Scottish water is meant to soften the yarn). These are manufacturers that concentrate on quality rather than fashion. Makes of this kind aren't usually found on the high street, nor online, but in the higher-end shops of the New Bond Street type such as Austin Reed, Burberry and Aquascutum.

I love what they can do for you - make you look perky when you're feeling down, soothe your body when you've had a tough day, hide your bad bits and accentuate your good bits. In particular, I have a love affair with fabrics - with real silk lingerie and soft kid leather shoes; with cashmere and fluffy angora knits; with scratchy Harris tweed and butter-soft suede.

But I am not, at all times, greatly enamoured of fashion.

One of the reasons is that fashion often sucks. When the trend turns to sack dresses with shoestring straps, where's a girl to turn? But another reason is that I'm a tightwad. If I buy a thing, and I love it and I look good in it, and I enjoy wearing it, I feel seriously aggrieved when fashion moves on and I can't wear my lovely item any more because it's 'old fashioned'. Keep it long enough and doubtless it'll be in fashion again, but you can't wear it a second time because it only reminds people how long you've been on the planet.

What are the options? Get it out once a year, stroke it and put it away again? Give it to someone younger? Chuck it in the bin?

One way to avoid that obsolete feeling is to wear vintage.

Vintage isn't for everyone but it greatly appeals to a certain type of woman - NOT being in fashion takes a bit of courage and it sometimes means you'll attract attention. It's not for shrinking violets. When you wear vintage, people often ask you where you got your clothes, or to turn around, or they feel your fabrics. When you wear it, you make yourself public.

Nor is vintage for people who are squeamish, worrying about whether someone's sweated into this clothing, or broken wind into it, or - good grief - died in it. Dear readers, if you had ever worked in retail and seen the filthy sweaty women who try on the clothes that are then sold as so-called clean and still have their tags, you would be less worried about this. The first thing I do with my new clothes is get the things dry cleaned...

Anyway, about a third of my wardrobe is vintage, and here's why:

* Vintage enables you to find fabrics that don't exist any more. Fabrics come and go in fashion and those of the Victorian era through to the end of the 1930s are simply no longer made. Fabrics like peau de soie and peau de peche and vintage satin bear no resemblance to their modern equivalents. 1920s and 1930s silk velvets are so fine you can pull a whole garment through a wedding ring, and come in the most wonderful colours - saffron yellow, emerald green, devores of all shades. Pre-1960s cottons have a higher thread count per inch than modern cottons and remain crisp and cool in the summer heat, while the gold and silver metallic laces and lames are beyond description.

* Vintage enables you to find techniques that are now rare outside the couture market. Fully-beaded dresses, fully-sequinned dresses, handknits with beading on every stitch, knitwear lined with organza or dupion. If you're really lucky and keep your eyes peeled, you might even get genuine couture at bargain-basement prices. I own several genuine couture items which would be well beyond my pocket if they were modern - my favourite is a trapeze-shape 1960s alpaca coat with nutria collar and cuffs, which cost £15. A similar one costs about £3,500 from Alexander McQueen.

* If you're petite, you may find the fit is much better. I am a shade under 5ft 2inches, which means I don't fit well into modern ranges other than petite (limited ranges and expensive). Luckily, I am handy with a needle, but reaching for the vintage racks means I don't have to be. In particular, garments from the 1950s fit like a glove, especially those with the three-quarter sleeves which were so popular back then.

* The quality of cut and tailoring can be superb. Even in day dresses of the 1950s and earlier, the seam allowances are enormous, making the garment more sturdy, the sleeves are properly faced, bodices may be fully lined and you tend to find French seams and clipped pinked seams rather than serged. When it comes to jackets and coats, the differences are enormous - properly weighted hems, Hong-Kong finishes, organza interfacing, prick-stitching.

Who can't wear vintage

Vintage won't work for everybody. In particular, it can be a problem with taller women unless they're thin and fine-boned. If you have a model's figure, the world is your oyster, but if you're broad shouldered or carrying any weight, your choice is more limited. Women have gotten bigger over the past 100 years and clothing before the 1960s was also worn over some form of corsetry, which shaped the figure from an early age. My friend M was slender but she couldn't even get her arms through the sleeves of one of my 1950s coats because the cuffs were so tightly tailored and her arms were inches longer than the fit of the coat. Nor would her broad shoulders or wide ribcage fit into my tiny jackets.

A tight fit doesn't apply to all items - the loose, untailored garments of the 1920s will fit many modern women and Victorian underwear is voluminous and fits almost everyone. 1950s 'trapeze-style' coats, which swing out from a narrow shoulder also fit most women - but broadly speaking, clothing of the rest of the 20th century can be problematical if you're over 5ft 6inches or above a UK size 10 (US 8). Pay particular attention to sizing if you're buying online.

The vintage market sells its goods by decade, so here's what to look for in each era.

Victorian era

White cotton, often hand-embroidered, especially voluminous nighties (good for full-figured women), bloomers and petticoats. Hand-made blouses with lace inserts (you'll need a tiny waist). Travelling costumes in wool or linen. Avoid anything black, especially silk - black silks were 'weighted' with iron salts which make the the fabric rot.

1910-1920

Pretty day dresses in cotton batiste or lace (very delicate). Tailored items in wool, especially gabardine. This was an extremely feminine era that used delicate fabrics and many of the clothes have not survived.

1920-1930

Evening gowns in beaded silk or cotton (store flat, never hang), lame items, devore velvet and silk velvet jackets. T-shirt-shaped blouses in silk, with beading. Evening coats and capes in velvet. Avoid gelatine sequins, which can't be washed. The average woman in the 1920s was not especially thin or small-waisted and designs are often quite forgiving.

1930-1939

Bias-cut evening gowns in lame or silk tissue, velvet gowns, velvet jackets, 'peignoirs' (negligees) in chiffon or velvet. Fairisle handknits. You HAVE to be thin to wear 1930s dresses - this was the era of the great slim-down and gowns made so tight you could barely sit down in them.

1940-1947

Tailor-made suits, CC41 (official Utility wear) items, including suits and coats. Evening gowns and jackets, often in black and shocking pink, with big shoulder pads. Avoid items that are overworn - clothing and fabric production was tightly regulated during the war years and many fabrics are of poor quality and have not worn well.

1947-1960

Suits, coats, tailored dresses. Day dresses with full skirts, especially in cotton prints. Mexican-style circle skirts. Cropped knitwear with three-quarter sleeves. Beaded knitwear. Sequinned knitwear. Trousers and capris with side zips. The 1950s was a very feminine era and generally requires a small waist and a largish bust. You can always pad the bust if need be, but modern women tend to have thicker waists than in the 1950s, when women routinely wore waist-cinchers.

1960-1970

Shift dresses and coats of a similar shape, usually in stiffish fabrics, including some synthetics. Beaded and sequinned knitwear. Ribbon knitwear. Capes. Avoid the cheaper synthetic items, especially nylon that has been washed many times.

1970s

Maxi dresses in bold prints, original-era Laura Ashley frocks in dimity prints, embroidered ethnic items.

I'm stopping at the 1970s because that's moving into an area when most of us either were, or became adults, and if there's one golden rule about vintage, it's don't wear it now if you were an adult when it first came out. It's borderline if you were a child, as I was in the early 1970s.

Where to find them

If you want to try wearing vintage, you can't beat visiting a clothing store and trying things on. Pay no attention to sizing - this has changed over the years and the label is unlikely to tell you anything you need to know, such as whether the garment will fit your ribcage.

It's very hard to get a good idea of vintage by buying online, and I'm wary of it myself even though I've been wearing vintage since the late 70s. If you do decide to buy online, make sure your vendor has a good returns policy, and pay close attention to the measurements given - most vendors give extremely detailed measurements. Err on the side of caution, if need be, and buy overlarge, and take the garment to a tailor for retailoring - you can always take a thing in, but don't expect to be able to let an item out.