[Just another Joe]

I tip well because it is a nice reward for doing well at a job that it is easy to do badly and hard to do well, it's not a bribe.

I pay the restaurant for the food. I tip for good service.
I just let the wait staff know ahead of time not to expect a good tip if I don't get good service.
For excellent service, especially if I see it happening to all customers, I will lay down extra.

[HairOfTheDog]

Its still weird to dangle money in front of people so they will treat you better.... IMHO....