Marty - AND your friend who never tips - could that be someone who also always complains about the service, size of servings, etc? LOL
Two weeks ago I had a late lunch at one of the restaurants that I used to frequent daily when I lived in town. The service was poor back then and has gotten progressively worse. When people ask me about the place I am frank and tell them the food is excellent and the service slow. SLOW? It was so bad this last time I took out a piece of paper and wrote on it "To (owners name) FOOD GOOD - SERVICE NON EXISTANT!" and did not leave a tip.
There are a couple of places that give me a 10% discount and I add that amount to my usual tip.