Having been a waitress (I won's say how many years ago!!) I always tip, usually 15-20%. I have been known to tip more for outstanding service, and less for very poor service (this has happened only once or twice in over 20 years). I've found the staff on the cruise ships to work very hard to make sure the guests have a great time and everything is to their satisfaction. I haven't been on a cruise yet that I haven't tipped more than the recommended amount.