Going on our first cruise from US I am now totally uptight about the tipping business. We hace previously sailed in the Med with British tour operators. The first time we were given envelopes at the end of the cruise to tip wait and room staff. After that tips were included in the fare and you could tip extra if you thought the service merited it. We did this. We are now sailing with princess and will have $10 each added daily to our account. If we get good service we may tip extra but I don't think you should "bribe" your severs by tipping in advance. Some of the tips given seem way too much to me.
Having read above all the people you are expected to tip on your way from airport via hotel to ship to cabin I am horrified. I think we will have to take out a loan!