Actually, most NJ'ers tip 15%, seriously. The ones you know who do 20% were trying to impress you. I tip depending on where I'm eating (buffets get less off the bat, since they just bring refills and bus....which I tend to do anyway having 2 young children and not being able to stand "clutter or mess"). If we are sitting down ordering different courses, I start at 15%, depending on how well they meet our expectations, we increase, but never decrease. For instance, if they are packed to the gills, I would take into consideration that I didn't get that refill as quickly as I'd like; however, if they are stark empty and I have to wait 10 minutes for a refill, well, sorry, but that's gonna cost you.