buffet is usually 5-10%, since the waiter/ress isn't doing much, plus, use your judgement.
i.e. you and 10 friends are at a table for three hours, ordering round after round of food, wine, spirits, and having a good time. any time I'm in that situation (hah...) I'd tip at least 20-30%.
fast food usually people don't tip, if the owner of the establishment personally serves you, do not tip (i.e. if Big John of Big John's BBQ Rib Shack makes your ribs himself, no tips. its viewed as rude in that case [can you say "bribe"?]).
5% for bellboys, 10% for room service, a buck or so for an elevator operator, and so on.
I hate etiquette.
speaking of which, the french invented "etiquiette"... once, some time ago, a french nobleman had guests. to avoid confusion, he had basic rules for conduct written on tickets (e tiquette) and given to the dinner guests . sonofagun. grumblegrumble