The only "TIP" I would give anyone who eats out is never, EVER, complain before the end of an evening, and if you have any sense, never, EVER, return to the said venue, as they WILL remember you, and make sure your food is the "CHEF's SPECIAL", with "SPECIAL SAUCE"...
21 years of bar/hotel/hospital repair work - I PROMISE you... you DO NOT WANT TO KNOW...
I knew one person who p*ss*d off some staff, so they kept a bottle of urine in the fridge, and always topped off his pint of lager with it... witnessed first hand...
It only gets worse... imagine the worst you can think of, and it has ended up on a plate of someone who has upset catering staff...