Well, I usually am on the receiving end of the tipping, so when I do go out, I always tip well. My minimum is 5 bucks, and I always tip at least 20% on anything.
I don't understand people who don't tip. Especially at restaraunts where the people are getting paid not by the company (something like $1.50 hourly wage) but by the customers and their tips. I have rarely encountered a waiter or waitress that wasn't any good, mainly because the way you are treated by them is directly proportional by how you treat them. So if you treat them like they are some kind of subhuman (which happens more than you realize) they WILL be offended. Remember, they are people too . . .