On the East Coast - a 20% tip is standard especially in NY and Boston - my son's ex-girlfriend put herself through college waitressing, so I know the score.. Wait staff in the US don't even get minimum wage thanks to some loophole in the law -- generally speaking they might get $2.50 an hour, and they get assessed for their tips when they come to pay tax which is often out of whack with what they actually get - especially in "this economy", so I tip and regard it as normal.
Just got back from Japan where there's absolutely no tipping - why can't everywhere be like that???
In a place like Charlotte which doesn't seem to be that Tourist friendly, a good tip which applies to everywhere in the US and Canada is to look for the local free weekly which you should be able to find in most restaurants and bars, it's a local TimeOut which gives all the listings, and often, surprisingly the quality of writing can be excellent as it's a place for hopeful journalists to make their first mark.
