I generally tip anywhere between 15 and 20%. I have only no-tipped a server one time, and it was last November on a trip to NYC. It took the waiter 30 minutes to get to our table. He didn't take our drink order, he barely spoke to us, ****ed our order up, the food sucked, and brought out the check with our food (which ****ING) pisses me off.
I wrote him a note and tipped him everything he deserved - $0