Please ignore this if I am being ignorant, but do you have a lot of these "Chain" restaurants? I can see being annoyed with the above when you're at a nice place, but for some of these chains (i.e. TGIF's, Applebees, Chilis, Outback, etc.) that's what is expected. The idea of these places is...
I always do too, but when you think about it, it's very odd - It's like you are almost bribing them for good service. It's so bad now-a-days, that the minimum tip almost seems degrading. It's just so weird to think that I have to over-tip in order to ensure exceptional service.
One other thing to mention to the wait staff: -Don't take anything out on your next customers. If the last party really screwed you out of a tip, it's not fair to take that anger out on the next party. How many times have I heard a wait person say "Ugh, I've had a bad day" or "The last table...