1. Remember, "when in Rome ..."
What do Margaret Atwood and Kate Moss have in common? They both understand that, as all readers of The Handmaid's Tale will remember, "context is all". True, Atwood did not necessarily intend her 1985 work of feminist fiction to be read for style tips, but the aspiring festival fashionplate would do well to bear her refrain in mind. I know it's beyond tedious for fashion editors to bang on about Kate Moss, but she always, always tunes her outfit to the occasion. She will wear mink and diamonds and her hair in a sleek bun to a gala, but don denim and wellies for Glastonbury. This is not about dressing up and then going casual: an equal amount of effort goes into each look. And it works. Contrast with Dita von Teese, photographed at Coachella last month picking her way across a field in a tight dress and white wedges, matronly handbag clamped to her side. Her vintage-mademoiselle look might work a treat on a front row, but looks totally wrong at a festival. I don't care if you've spent four years perfecting your signature style: if it's not festival-friendly, leave it at home.
2. Forget the catwalk and dress according to the weather forecast
Miuccia Prada once explained that when getting dressed, she plans her outfits from the feet up: she decides what shoes she wants to wear, and then fits her clothes around them. This is sage advice for all festival-goers, as you will be at the mercy of the elements. To simplify things even more, remember that there are three - and only three - acceptable modes of footwear for festivals in 2009. Wellies if it's wet, flat gladiator sandals if it's hot, and Converse if it's in between. Once you have ascertained which of the three you need to wear, you can plan the rest of your outfit around that. Easy.
3. Avoid looking like a clone
The idea is to look as if you are dressed for a festival, not like everyone else at the festival. To this end, avoid wearing anything from the Kate Moss Topshop range, unless you want to be one of a small army of Kate-a-likes. Also, resist the temptation to wear anything from the Matthew Williamson for H&M range as this, too, will be standard-issue for festival posers this summer.
4. Never, ever wear fairy wings
Grown women wearing fancy dress fairy wings: of all the festival cliches, this is the worst. The intention, one assumes, is to convey some sort of subversive-feminine, Courtney Love vibe, but the effect is winsome and not a little tragic. Runner-up in the category of most annoying festival cliche accessory: cowboy hats. So five years ago. If you really don't feel dressed without a bit of dressing-up-box action, then this year is all about a feathered headdress, or a Stevie Nicks-esque shawl.
5 (a) The first principle of high-impact dressing: get the silhouette right
Dressing for a crowd situation is totally different from dressing for a dinner date. Couture-style detailing/fabulous quality fabric will get you nowhere. You need to get the silhouette right, and then you need to dial up the extras - colour, fabric, detail are all secondary to that. First, the shape: smock-and-leggings is over, I'm afraid. This year, you need a waist. A T-shirt tucked into high-waisted shorts looks set to be this season's mock-and-leggings.
5 (b) The second principle of high-impact dressing: accessories speak louder than words
Brightly coloured comedy sunglasses are still shorthand for crazy-festival-chic, but brightly coloured gladiator sandals (see Kate Bosworth at Coachella) are one step ahead. (Flip-flops and Birkenstocks are over.) Black 80s Wayfarers are still the slightly less obvious version. As for handbags: this is probably the one occasion on which your outfit will not be enhanced by a Chanel 2.55 quilted classic. A messenger-style bag is the best festival option, unless you are brave enough to early-adopt the burgeoning bum-bag revival.
6. Don't get stuck in a festival timewarp
Just because you're an old-timer, don't think you can get smug and snigger at the newbies in the wrong wellies. Just because you wore something last year, doesn't mean it's going to work this year: 12 months is a long time in fashion. As a rule of thumb, the trends from two to four years ago are the ones to avoid: little black "rock chick" waistcoats, for instance, have had their day.
7. Neither tents nor wellies should have flowers on them
Festival chic is all about looking like a veteran: that I-practically-grew-up-backstage-at-Glastonbury angle, even if this is your first day- trip out of suburbia. Having great big pink pansies on your tent, wellies or anorak immediately marks you out as an amateur. Classic Hunter wellingtons in green, black or trawlerman-yellow are to the festival field what Jimmy Choo sandals are to the party circuit: dependable, comfortable and classy. If you can't resist glamming it up, this season Hunter and Jimmy Choo have joined forces to produce a limited edition, crocodile-effect wellington: counting the pairs backstage promises to be this festival season's new fashion-spotter sport.
