A survey showed that 38% of British people would never complain in a restaurant – however bad the food or service. Who can blame us for our reticence? Chefs are sometimes unhinged. Marco Pierre White ejected diners who asked for salt and pepper. His protege Gordon Ramsay created equally priceless PR for dispatching an American customer who had, he said, the temerity to ask for tomato ketchup with a dish of red mullet and summer minestrone.

Waiters seem less threatening, but can be sneaky. In Waiter Rant: Thanks For the Tip – billed as a front-of-house Kitchen Confidential – Steve Dublanica tells of restaurant staff putting laxatives in soup or using a returned burger as an ice-hockey puck before taking it back out and serving it again to the customer.

These are, we hope, extreme and rare reactions, but to guide a path through the minefield, we enlisted the help of the legendary Fred Sirieix, unflappable general manager of London's Galvin at Windows.

Be clear. Be concise. Be calm

OK, you have a legitimate, non-subjective complaint: the dish is not the one you ordered; the food is cold when it shouldn't be. Alert your waiter immediately and, this is important, explain the problem without bluster, exaggeration or threat. There should be no reason to raise your voice at this stage. Mistakes happen; allow the restaurant to correct it.

"There's a difference between a complaint and a comment," says Sirieix. "Somebody can make a comment and say: 'I thought the service was a bit fast.' Or 'I did not get the table I wanted.' People are in business like we are and they feel a responsibility to tell you, because they would want to be told themselves. That I am very happy to know."

Know your onions

Before you kick off in a restaurant, take a moment to check that you are not going to embarrass yourself. Sweetbreads are not what they sound like, and neither is head cheese. Hot-smoked salmon has an all-important hyphen and can often be served cold. "Some people order ceviche and say, 'the scallops are raw,'" notes Sirieix. "And I will say, 'Yes sir, it's the ceviche.' What can I say?"

Speak now, or forever hold …

Do not complain about a dish when you have eaten most of it – say something straightaway. Equally, if you have not enjoyed an aspect of your meal, it is good manners, and karma, to alert someone while you are at the restaurant, rather than venting your fury on Twitter, TripAdvisor or elsewhere.

A salutary tale: last December, a food blogger called James Isherwood didn't particularly enjoy his starter at Mayfair's Hibiscus and wrote an unfavourable criticism of it when he got home. He woke up to a stream of abuse from the chef concerned, Claude Bosi, with fellow two-Michelin-starred cooks Simon Rogan, Tom Kerridge and Sat Bains jumping to Bosi's defence under the hashtag chefsunite. Bosi's justification was that Isherwood was asked about his meal at the time and said nothing.

As the Times restaurant critic Giles Coren wrote in his book, How to Eat Out: "Once you walk out of the door, it's over."

That said…

If you feel your complaint has not been taken seriously, or you remain disappointed with your experience, hit them online. Internet reviews – good or bad – are increasingly powerful for all restaurants; no one in the trade ignores them. "I look at everything all the time," admits Sirieix.

Don't go fishing for freebies

Maybe it's the recession, perhaps we are over-excited after years of suffering in silence, but it is still the prerogative of the restaurant to suggest how to make amends for a complaint, not you. You may be pleasantly surprised. Any decent restaurant will know that if they can turn your criticism into a positive experience, they may retain your loyalty for ever.

"A customer has to complain with honesty and integrity and have high values attached to it," says Sirieix. "If you're just saying something to get a free drink or a free meal, we can see what you are trying to do, you are not going to get it. It won't happen."

Don't believe the horror stories

Tales of restaurant staff tampering with your food once you have sent it back are mostly apocryphal. We live in litigious times and the Food Standards Agency is just a phone call away.

"I'm sure there are sick people who do things, but I've never worked with them," says Siriex. "If I did, it wouldn't be for long."