If you've ever been rude to either of these women, look out – you might find yourself served up as satire

Next time you want to complain in a restaurant, stop for a moment, take a deep breath, and do it with a little grace. You might think you have carte blanche to behave as you wish if you're dropping a considerable wedge of cash in an upmarket restaurant, but the waiting staff will be watching your every move.

Especially if they're as imaginative as Anna Magnowska and Laura Quick, both experienced waitresses, who discovered that dissecting the weird, wonderful and often downright rude customers was a great way to unwind after a long shift in the Sydney restaurant where they worked in 2002. The pair are also illustrators, and soon began to record their observations on paper, a hobby that has developed into an exhibition of their artwork, opening in London's Shoreditch this weekend.

The images are hilarious, at times vicious, and often shameful indictments of the way hospitality staff are treated while on the job: "Kinky Man" wanted to wear Quick's apron. She has drawn him wearing a suit with no facial features apart from a cavernous mouth as he yells: "I bet you're as kinky as me". Then there's the businessman who dreamt of fleeing the world of finance for a pastoral idyll, taking his serving girl with him. "I can see you riding a horse," he told Quick. "Yes, riding. Through the hills of Gloucestershire. Do you ride horses?"

If it sounds like Magnowska and Quick despise their job and their customers, that couldn't be further from the truth. "You do see some of the worst in the images we've done, because that was the only way we could express just how obnoxious some of these people could be," explains Magnowska. "But it was about getting the essence of the person and our own frustration out through the pencil. We don't always draw the worst or the rudest person. Often it is people we find interesting or intriguing, who perhaps have a sinister or slightly pervy undertone.

The pair continued waitressing on their return to London, working in a number of City restaurants frequented by financial Fat Cats and traders eager to celebrate the day's mega deals with magnums of Cristal. But all the rowdiness, bum-pinching and inappropriate propositions haven't put them off. They are clearly very fond of some of the characters in their exhibition, even sympathising with the man who fantasised about Quick riding a horse. "I got the impression he was a looker in his day and wanted to find a younger lady to relive his lost youth," she says. "You get that a lot with middle-aged men who want to feel young again. You're there being servile at their beck and call, and you feed their need to feel sexual and be predatory – often in front of other businessmen."

Even though both could give up waitressing to focus on their illustration work, they wouldn't be without it. "We're in a privileged position to be privy to many different kinds of people's social lives. You see people when they're relaxed, when they're drunk and when they're trying to impress – all kinds of human behaviour," says Magnowska. Quick found her drawing became less interesting when she gave up waiting tables. "Even if it's only for a few hours a week, I need to feed my mind."

So what is the best way to react to unruly customers? The furthest either woman has got to enacting revenge on an unruly customer is when one drunken businessman tried to grab Quick's hand and kiss it every time she walked past. She rubbed some chilli on her hand and watched him disappear for a long toilet break after the next time he slobbered all over her. Quick still feels a little guilty about this incident. And you certainly won't find them spitting in your soup any time soon. "I've seen steaks being washed if they've been on the floor," admits Magnowska, "but you'd have to be a bit of a sociopath to actively spoil somebody's food with your own bodily fluids."

Here are the pair's tips for being on your best behaviour next time you dine out.

How to order

Don't worry about changing your mind just as the waiter leaves the table, but wait until the order has gone through to the kitchen and you might mark yourself out as a troublemaker. Think twice about sending something back saying the waiter has made a mistake with your order in cheaper places and chains – they might find their pay docked as a result, and will probably have been on less than minimum wage in the first place.

Magnowska and Quick have watched many bankers trying to impress their colleagues by ordering expensive wines – never anything from the first half of the menu – even though they would inevitably end up on JD and cokes. "The excess was crass," says Quick. "They probably didn't know what they were drinking. Things might change given the current financial mess, so our exhibition documents that era. I think it's quite fitting that we're shaming these bankers."

How to complain

Simple: be polite. If the wine is corked, it isn't the waiter's fault. Nor is it his fault if the food is undercooked. "One customer was particularly aggrieved that the place I worked in didn't serve chips," recalls Magnowska. "He started screaming, 'You're a fucking waitress! What do you mean you don't serve chips?' He acted as if it was my decision not to serve chips. I think I was quite rude back, but he got chucked out in the end because he was insulting everyone."

If you have a valid complaint you should be offered something to make up for the shortcoming. "If people complain and you give them a glass of champagne, they're always 10 times more grateful when they leave," says Quick.

Make sure you haven't got any food stuck in your teeth when you make your complaint. "If you have spinach stuck between your teeth any complaint is pretty much null and void," she laughs.

Big groups

Large tables usually present the most problems for waiting staff, especially at Christmas parties. Make their lives easier by remembering what you've ordered, and try to stay in the same seat so as not to confuse them further.

"I love Christmas parties where everyone arrives from the office all prim and proper and professional," says Magnowska. "Before long they'll be ordering trays piled high with shots."

Interacting with your waiter/waitress

Shouting, waving or clicking your fingers to get a waiter's attention are all sure-fire ways to annoy them. If, on the other hand, you feel you are being over-attended to, state your position politely and you should be left alone. "If people want to have a meal where they aren't interrupted, of course I respect their right to do that," says Magnowska. "It's best if you say, 'We're fine for now. We'll give you a shout if we need anything.'"

Do place your knife and fork together once you've finished eating. It's the only way a waiter can tell you have finished.

How to tip

Many waiting staff earn below minimum wage and rely on tips, as The Independent's Fair Tipping campaign revealed earlier this year. "Sometimes people really want to know about the tipping policy and where it goes," says Quick. "But others react really badly, thinking they are being guilt-tripped into paying a tip when 12.5 per cent is added to the bill. If people leave coins, I say, 'Excuse me, you forgot your change.' They're usually embarrassed."

"One guy left me an enormous bouquet of flowers once because he forgot to tip me – along with his mobile number."

The perfect customer

Despite all their time spent musing on customers' negative characteristics, Quick and Magnowska have found a little time to reflect on their ideal client. "Someone who knows how to dine: they would have an aperitif, know what to order and enjoy their food. They would take their time, choose good wine, and ask your opinion just the right amount, to show they respect your knowledge. They'll round it off with a nice malt whisky."

Just Desserts: The Waitress Strikes Back, 15–30 November at Gallery 32, Charlotte Road, London EC2. www.justdessertspreview.com. The exhibition is part of the SAVE Shoreditch Campaign, which is raising money to promote responsible regeneration in the area. A percentage of each sale will go to the campaign