I was watching 3rd Rock from the Sun today, and Sally said exactly what I've wanted to say to a LOT of people. Enjoy.
Sally: Woah. Let me ask you something. Was your service quick and courteous?
Man at table: Yes.
S: Was your food hot and exactly what you ordered?
...Then why is it, my friend, when I subtract your check from the amount on the tray that I come up with 97 cents for me?
I didn't think you'd count it in front of me.
But you're glad I did, now aren't ya?
Because now you understand that a tip is short for gratuity, and gratuity is short for gratitude.
I never heard that ma'am.
Don't interrupt me. Gratuitude for a job well done. Now 5% is not gratitude, Mister. It's an invitation to an ass-kicking.
If you're still confused about how to treat your server, here's a chart for beginners.