Fashamatics, or how to solve the dress code equation

There's a useful formula for the desparing fashionista playing the game of past, present and future.

The spring/summer ready-to-wear season, coming as it does in September and early October when temperatures in New York and European capitals can soar to 30°C (add another 10 for hot interiors), poses a serious dilemma for fashion show guests.

What on earth to wear when it's simply too hot to embrace the new autumn/winter season? And yet to revert to the season just passing would be equally unthinkable! There is nothing more passé than Prada stripes in September when they first appeared in Vogue in March.

The answer is to play it safe; wait until you get an idea from the catwalks about what we are all going to be wearing in six months' time - from the looks of things at last week's New York Fashion Week, it will be the colour orange, 1930s-style prints, a tailored take on sportswear - and start working this into autumn trends, such as the midi skirt, patterned satin blouses and red pointy toe heels.

Playing this game of past, present and future, cherry-picking trends, subtracting any remnants of last season and adding something "catwalk hot" (teaming pale grey with a flash of orange), I call "fashamatics", or fashion maths.

This is when you divide the distant future by the near future to get a sum of where we are right now. Here lies the answer to the fashion show dress code.

There's slightly more to the equation. It involves the logistics of what your clothes are required to do in a day. The first show starts at around 9am. You might find yourself sitting in an airless basement waiting for the last one to end at gone midnight. Then there are shop openings, post-show parties and dinners, all of which inevitably involve queuing and travelling to and fro. Have you tried running for a taxi in heels?

It's also vital in the midst of juggling seasonal fashions to retain a sense of personal style. One person who seems able to carry all this off without looking like the proverbial fashion freak is Anna Wintour.

For decades, I've watched the US editor-in-chief of Vogue wear pretty much the same style year in, year out and yet manage to remain the number one authority on clothes.

Last week in New York was no different. Her uniform of knee-length flippy skirted dress with short-sleeves (to show off enviably toned arms), kitten heel sling backs, sunglasses, H Stern diamond necklace and of course, bobbed hairdo, still made a statement. Her dress was orange. A day later, everyone wore orange.

One day, I'd like to take the British anthropologist, Desmond Morris, most famous for his 1967 book The Naked Ape, to a fashion show to see what he'd make of the fashion pack instinct with its alpha females and strange tribal ways.

Here, magazine teams stick together like wild herds, following each other around and even dressing the same. (It's not uncommon to hear people saying, "You look very Elle today," referring to a poncho/hairdo/shoe style.)

It's no accident that when you start out as a fashion rookie you are seated in the very back row. This gives you a chance to study the pecking order and decipher the dress code (which is good because from here you rarely see any more than the tops of the heads of models gliding down the catwalk).

Although certain editors travel to the European shows armed with a fleet of Louis Vuitton trunks (US Vogue's Hamish Bowles and the grand doyenne of Italian Vogue, Anna Piaggi, to name but two), many others travel outrageously light. The latter adopt a strategy of sticking to a uniform that can be dressed up via natty accessories.

Katie Grand, the stylist who has collaborated with Marc Jacobs for many years, wore huge orange bug-eye sunglasses during New York Fashion Week. Did she plan her outfit with military precision or throw it together that morning? Who cares? It's image makers such as Grand, Alexa Chung and Susie Lau who have become crucial to style-watchers because they often precede (or inspire) runway trends. The first time I saw Ugg boots was on a fashion editor recently returned from an assignment in the Australian outback.

School ties worn by Japanese stylists, I seem to remember, became all the rage one year. Trilby hats were popular with Italians in another. The colour brown struck a chord in Milan once. Breton stripes and coloured friendship bands, unearthed in London, went on to become global fashion trends.

So although I can't wait to see what designers have in store for us over the next few days, weeks and month ahead, I'm going to be taking notes about what I see directly all around me as well. And you'll be the first to know.