I usually tip 15 percent, and someone has to really screw up not to get it. I know they depend on it. So, this helps people who are at the mercy of the kitchen or mgt. rules that had intentions of giving better service but weren't able to do so through no fault of theirs, but it also rewards people who bring me the food after a long wait or otherwise displease. However I don't require much besides the minimum. Give me a pitcher of water instead of hovering around. Besides delivering the food, I don't want to see someone visiting me, and certainly not constantly asking me for a response about "Everything OK?" while my mouth is full. I want to be able to catch the waiter/waittresses eye when they are between tables without much difficulty, but I don't want them coming to me unless so signaled.