It is a humid Monday evening and anyone who is anyone in the world of contemporary art is heading for Art Basel, the giant art fair which, every June, floods the pretty Swiss city with the most important dealers and collectors, and all the advisers, agents, envoys, runners and assorted gawpers who occupy the zone in-between them. Dozens of private jets are parked on the tarmac at Basel airport. On the outskirts of the city, looking out over immaculate Swiss fields, the Beyeler Foundation – a Renzo Piano building filled with the best of Ernst Beyeler’s celebrated collection – is hosting the opening party that traditionally kicks off the fair, an event sponsored by NetJets, suppliers of private jets to the very wealthy.

The place is heaving with multi-millionaires. An anxious-looking Jay Jopling hovers at the entrance with a mobile clamped to his ear. Andreas Gursky, the German photographer who recently sold a photograph at auction for £1.7 million, is talking earnestly to a group of German collectors. Norman Foster waltzes in wearing a crisp suit and bright green tie. As he plucks his first glass of champagne from a tray, some tall, tanned beauties launch themselves in his direction. Norman Rosenthal, exhibitions secretary at the Royal Academy, wanders through with a young shaven-headed Chinese artist in studded black leather.

All around, a curious form of theatre is being enacted. The big-hitting dealers are there – Matthew Marks, Christophe van de Weghe – working the terrace, because many of the really serious collectors are mingling here too. These are very bright, sophisticated, energetic and focused people, mostly men, who have made a great deal of money, typically in the worlds of finance or property development, and are now keen to direct their energies into the business of art collecting. Inevitably, their business activities shape their collecting attitudes and habits. There is an element of rivalry, an additional frisson of competition as to who will sniff out the next undiscovered name or scoop the next big art trophy to display on their walls.

Information is being exchanged and processed at speed: mobile phones buzz, BlackBerries are glanced at rapidly. The talk is of the Venice Bienale, from which many of those present have jetted direct. Then Basel is rapidly followed by Documenta, held once every five years in Kassel, Germany; Sculpture Projects in Münster; and the Grosvenor House and Olympia art fairs in London. For the really committed, it will be a sensory-overloading rush from one to the other. As David Teiger, a collector from New Jersey puts it, “I was already exhausted just getting ready to go: practising staying semi-alert without sleep, searching for stimulants that can pass airport security…”

He will need them, because Tuesday is as intense as it gets. The day dawns hot and sunny, and in the vast Basel convention centre, 300 galleries from all over the world are readying themselves for the first and most important of many openings, their 50sq m booths filled with the best show-stopping art they can muster. This morning’s “First Choice” preview is strictly for big-hitters, the “Basel VIP” class. On the ground floor is the well-behaved art: Waddington, Cheim & Read, Marlborough and Timothy Taylor galleries. Upstairs is the edgier work. White Cube has a range of choice pieces by Gilbert & George, Antony Gormley, Tracy Emin and Damien Hirst: not the £50 million diamond-studded skull, but a diamond-shaped painting with butterflies.

At 11am, the doors open and a surprisingly undignified rush ensues. Large numbers head for White Cube. “Can we hold this for an hour?” ask a middle-aged couple gesturing urgently at the Gilbert & George. A gallery assistant in cocktail dress and towering heels nods calmly, and the agreement is noted in a book. Someone else wants to know about the Doris Salcedo. Jopling starts to explain, then his phone rings. As he is relaying a price on the Emin, another couple want to know about the Gormley. “Are we using red spots?” Jopling asks a colleague. Apparently not. “Oh yes, we’ll sell it all,” another assistant assures me. “Things move very quickly.” She turns sharply and muffles a yelp as someone steps backwards to view a large painting and into the arms of the standing Gormley figure.

A similar feeding frenzy is going on elsewhere and the fair has only been open for half an hour. Some galleries have revealed to their best clients what they have; some have accepted advance reservations on pieces, and stories abound of collectors sneaking in early disguised as cleaners or workmen in order to scout the best pieces before their competitors. “The frenzied atmosphere in the first few hours always amazes me,” says Felicity Waley-Cohen, vice chairman of the Serpentine Gallery, a calm, still point in the heaving throng of the Gagosian booth. She is admiring a black plastic rubbish bag dotted with cotton wool made by Tom Friedman.

“Nine hundred?” squawks an incredulous American buyer, staring at a piece of twisted metal tubing. “Is that nine hundred thousand? And what currency are you quoting?” With galleries operating in pounds sterling, US dollars, Swiss francs and euros, the potential for confusion is great. No galleries display prices, and the most icily exclusive, like Gagosian, don’t even display labels. The implication is clear. If you have to ask how much something costs, you are not really worth talking to.

Malcolm McLaren wanders by unrecognised. The dealer Kenny Goss, George Michael’s partner, is here wanting to buy a Gary Hume. Nastassja Kinski is just looking. A group of Texans is admiring a video piece focused on some red lips and a tongue. “Now why do you like this? Why is it important?” asks Mark Fehrs Haukohl. “OK. It’s fun. It’s humorous. But does it go to the next art historical level?” It is a good question, which might usefully be applied to the empty black plastic bin-liner with metal rim on sale at the Italian Noero Gallery for US$8,000 (£4,000), or the installation of two spinning car-wash brushes at the German Klosterfelde Gallery for £15,500. Fehrs Haukohl is president of the Vero Group and he is acquiring museum-quality work by women photographers of the 21st century for his collection in Houston. He poses happily beside a Juergen Teller photograph of a semi-naked Kate Moss. He has a clear philosophy for his collecting. Other buyers feel they need advisers to help steer them. This may be because they recognise that they have no taste, or because they are too busy to follow the market and need an extra pair of ears and eyes on the job.

David Roberts, a young, unshowy Scottish collector who has made his money in property developing, prefers to trust his own instincts. “I don’t have a degree in art history; I just go on gut feeling. I’ve been coming to Basel for the past five years and it’s very good, but I hate the competition, the rushing in at 11am, the business of ‘Have you seen such and such?’ I hate being part of a group.”

Roberts started buying 15 years ago, but in the past five years his collecting has gathered pace, and philanthropy now plays a growing role in his decisions. “The collection got too big for our house – one of my installations is 28m long. So I bought a space in Great Titchfield Street in London.”

The gallery, 111, will open in September, but he will lend the space from time to time to groups of young artists so that they can use it to sell their work and take 100 per cent of the profits. (Dealers typically charge 50 per cent.) He has also bought a second, larger space in Camden that will be used to show the bigger pieces in his collection, and Roberts is one of a rare breed of British collectors who is already giving works to public art institutions and contributing to their acquisition funds.

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