I just can't imagine NOT tipping for the wonderful service I've received!! We prepay our tips and then also do something special for the ones who went above and beyond.
Last cruise, in addition to the standard tips prepaid we also gave a bottle of Hennesy to our waiter (his fave), an xtra $20 to his asst, and an xtra $20 plus some books I was reading to our steward (we shared the same likes in authors). All the extras were accompanied by cards telling them how great our cruise was THANKS TO THEM!
We also gave cards and smaller items to our hostess and bar waiter which we don't always do but on that cruise they really went out of their way for us!
October 1997 Princess (Bahamas)
October 2000 Carnival Tropicale
October 2006 Carnival Miracle
October 2009 Carnival Legend