I *ALWAYS* tip... if the service is excellent, I will tip well enough that I will be remembered the next time. If the food isn't right, that gets brought to their attention immediately. I don't have a problem with asking an excellent server if they have to split their tips. If they do, I will slip the server an extra 10 bucks or so.

Always treat servers and waitstaff well, tip well, and they will take care of you next time.