When even the smartest style magazines start to refer to the "nouveau poor", it's clear that fashions and consuming passions are heading in a new direction. After last season's sombre chic and austere mood on the catwalk, there's a "make do and mend" ethos for spring/summer. "In these hard times, dress up," instructed Vivienne Westwood in the notes to her Gold Label show, before suggesting you consider wrapping yourself in a tablecloth. When the glitterati turn to their soft furnishings for inspiration you know that we mere mortals are also but a hop, skip and a giro away from throwing in the fashion towel. Or at least making ourselves a new dress out of it.

"Style never has to suffer," declares Calgary Avansino, executive fashion editor of British Vogue. "It has nothing to do with how much money you spend. Women just have to be more creative about finding smart buys and styling them well."

The latent creativity in many of us has been suppressed for so long by the phenomenon of "fast fashion" – whereby a whole outfit could cost you less than your bus fare to the shops – that we have forgotten what it is to buy clothes as an investment or to re-work pieces from the backs of our wardrobes. "Keep a dash of lipstick on the stiff upper lip, and give up the fatal vice of cheap clothes!" counsels a 1933 issue of Harper's Bazaar, and the advice echoes from their Depression to our recession. So use your imagination, not just your credit card, and before you try on new clothes, try out these tips for size.

Where to start

Continuous "drops", as the arrival of new stock at high-street shops is known, mean that our perception of seasonal dressing is almost non-existent. With fresh styles arriving in stores on a weekly basis, we have become used to picking up new items as often as we can, with little regard to our bloated cupboards and parched purses. As the weather turns warmer, it isn't our wardrobes that need an overhaul, but our shopping habits. "People are fed up with disposable stuff," says Amanda Slader, chief fashion adviser at John Lewis. "They're looking for items that will last a whole season and rejuvenate existing bits. Some may say frugal isn't sexy, but it's just different from what we've got used to."

Slader has more than 2,000 clients on her books at John Lewis and is heading the chain's new "Fash-Efficiency Classes", where customers come in, under no obligation to buy, and learn a new and more crunch-friendly style of shopping. "We take a look at what they already have and could be making use of," explains Slader, "and on the back of that, try to identify one or two key pieces that will really get their look on-trend and up to date. We don't work on commission, so we're not under pressure to make people spend money."

It's part of a re-education of shoppers that is gradually coming to the fashion fore. Blogger Kathryn Finney set up her website, thebudgetfashionista.com, in 2003 – "before budget got cute", she jokes. "At that time a lot of stuff was being thrown at us – you had to have the new It-bag every six months and the new Marc Jacobs boots. I was trying to figure out how to marry wanting nice stuff with the need to pay my bills." Finney has since published one book and is currently working on her next, and her site has become a focus of the budget-shopping community.

Now even Vogue has relaunched its cult "More Dash Than Cash" section. "People are getting smarter about every penny," says Calgary Avansino, "so what could be better than learning the tricks of the trade? Getting quality catwalk looks at high-street prices is exactly what people are craving right now." With their combination of shopping suggestions and styling tips, the new pages mark a change of direction: it isn't what you can get any more, so much as what you can do with it that counts.

How to buy

In the spirit of homespun economy, start your shopping trip chez vous and look through the clothes you already have. There will be things you can customise or have altered – turning trousers into shorts, for example, or having darts put in a dress to give it a different fit – which are cheaper than buying a new item. But first edit out things that don't fit or that you'll simply never wear: "If you haven't already made a piece work, you're not going to," says Slader. Just looking through things you may have forgotten about may be enough to slake your sartorial thirst for the time being. Luke Wohlgemuth-Browne owns the London vintage store Stromboli's Circus: "We all have items which can be worn again in a fresh way by adding different accessories. And if your parents still have some of their old clothes, root around and see if that old cardigan or 1970s dress will help transform your winter wardrobe into fresher springtime looks."

Once you're in the shops, stick to a strict "cost-per-wear" rule: the price of an item divided by the number of times you're going to wear it in a given period. New Look's bouclé jacket (as modelled by Alexa Chung) costs £45, and is versatile enough to wear to your desk or on a date. Jane Fletcher is head of design for the brand: "It's very important that we provide value, whether it's in price or a point of difference, like embellishment or detailing." At three wears per week over three months, the jacket works out under £2 a time.

"We're all amateur economists these days," comments Kathryn Finney, "Cost-per-wear makes us focus on utility and value. If something's only £5 and you don't wear it, that's £5 wasted."

So, if shoppers are concentrating on value and usefulness, does this mean that "trends" as we have known them are over? "No," says Slader, "we're saying invest in new classics that will highlight what you have, like this spring's 'boyfriend cardigan' that you can belt over your old floral dress. You can reflect a season without having to buy masses." Avansino agrees: "People want to feel they are making a worthwhile investment; we saw this on the catwalks at the most recent shows with designers providing 'the best' blazer or 'the most classic' coat." Her tips are to make sure you have a statement necklace (try Freedom at Topshop), and she praises Warehouse's boyfriend jeans. Top off with a strong-shouldered blazer, and you have this season's key pieces that will work with what you already own.

Where to go

Roger Walker-Dack has been MD of Designer Warehouse Sales for 22 years. The company hosts regular events in London at which shoppers can pick up pieces from the likes of Martin Margiela, Nicole Farhi and Vivienne Westwood at up to 60 per cent below the original prices. "Go to places that are used to discounting clothes," he advises, "you'll find the bargains are getting better and better." Similar warehouse events happen across the country, so check the website (dwslondon.co.uk) where you can also find tips on how to navigate the vast sales.

Listings magazines also carry details of sample sales and vintage fairs. "I like the Alexandra Palace fair and Portobello Road for special items," says Luke Wohlgemuth-Browne. You can also try hosting swap nights with friends or attending "swishing" parties (see swishing.org), where you pay a small fee to offload your unwanted items and have a dig through other people's.

Oxfam launched its flagship boutique in London's Westbourne Grove last May, and others around the country will follow this year. I left the London store recently with a pair of Bally shoes (£12), a Chloe shift dress (£12) and a Burberry mac (£60), but they also stock a wide range of second-hand high-street pieces at great value prices.

Vintage stores also offer a level of quality that recent fast fashion has erased from our memories. But remember that the key to shopping on a budget is imagination and individuality, so don't be afraid to look at new styles or trends. Use the cost-per-wear equation and keep impulse buys to a minimum, and you're guaranteed to come off well in the long run. The fashion illustrator and artist Julie Verhoeven is an expert in idiosyncratic style and is known for her kooky, eclectic look: "I often find interesting accessories in party stores," she says. "And theatrical make-up suppliers are great place for experimenting with colours. Finally, invest in some red shoes – they lift an outfit and inject style. Less Home Counties and more razzle-dazzle!"

And if you still find yourself trawling the shops with your beleaguered bank-card, simply click your heels together and say, "There's no place like home."

The John Lewis Fash-Efficiency Classes are now running nationwide, 08456 049 049 for details. The Designer Warehouse Sale is on this weekend; see dwslondon.co.uk for details