I'm with you slip, I can't leave without giving at least something. Generally, I give a fairly large tip, because waiters (and waitresses) have to put up with a lot of shit their whole day, and I think my tip might improve their day a tad. If the service sucked, the tip would be much less. The quality of the food has very little impact on the size of my tip, because it's not the waiters fault the food sucks..