my grand parents did it, my parents did it, so i do my damndest to try for 15% average, 20% above and beyond. if it its bad service ill simply leave a buck for them. my brothers ex grtilfriend worked in resturants as a waitress for a few years. i saw soem of the customers she had to deal with, so i always try to remember that the waiter/waitress has probably had a PITA Customer who thought they were better then the world.