Most of the PP's have covered the tipping situations--cashless ship (you can apply cash/gift cards to your account if you don't want to use credit), not tipping every time you eat, etc. I just wanted to add more info about the 'automatic' gratuities that get added to your account at the end of your cruise:
$12/person/day gratuity breakdown:
- $4 Stateroom Host
- $4 Server
- $3 Assistant Server
- $1 Head Server
As others have said, that amount can be adjusted up/down at guest services--but that is a cruise industry standard tipping amount. You will receive tip slips and envelopes at the end of the cruise with the amounts each person will be getting. If you have a credit card listed on board, it'll be charged that way. If you want to add more money, you can add additional cash to the envelope for that person.
Enjoy your cruise!