What kind of tip do you leave in the following situations:

- Nice, high-quality dinner buffet: attentive waiter provides drinks (including bar drinks), promptly removes dirty plates, and otherwise provides full-service with the exception of bringing the actual food.

- Average-quality lunch or dinner buffet (such as a casino buffet): waiter serves water, soda, and tea (no bar), maybe takes the plates away if he's feeling like it.

- Breakfast buffet (such as what you find at a mid-range hotel): waiter brings you juice, coffee, and water, and you don't interact with him/her again, except to pay the bill in some cases.

I tip the normal 15% of the meal+bar cost for a fine buffet with good service. At casinos or mid-range hotels, I leave about a buck per person.

Is 15% too high? Is a buck-a-head for juice or a Coke too low? I imagine that waiters/waitresses hate working buffets...I'm curious as to what other people do.