The only thing I ask of a waiter or waitress is to attend to me in a timely manner. I don't expect the food to reach my table within five minutes of placing the order but I have limits. Thankfully I can only recall one time that my server took forever.
There are differences with each new server. Some will be somewhat reserved while others will be checking on you every two minutes. In all cases I leave a 15 percent gratuity. It's only been twice (that I can remember) that I've left a big tip: once at a late dinner on New Year's Eve, and at a local restaurant where a family member got ornery with the waitress.