Let me say first that I try to tip pretty good, between 15 and 20%. If we drank water and the glasses were kept filled, I try to add a little more.
The question I've always wondered is why we base the tips on the total bill and not the work performed? Why should the person working at an expensive restaurant with a lot of help - busboys, runners who deliver the food, etc. expect a lot bigger tip than the waitress at waffle house who's busting her butt doing everything but cooking?