There are three different ways tipping is handled on cruise lines:
GRATUITIES TO BE PAID DIRECTLY TO SHIP STAFF:
In these cases the cruise lines will place tipping guidelines and tip envelopes in your room to be given to ship staff on the final night of your cruise. Lines that follow this procedure include Royal Caribbean, Celebrity and Disney.
GRATUITIES ADDED TO YOUR ONBOARD ACCOUNT AUTOMATICALLY:
These can be settled at the end of your cruise and can be increased or decreased at your discretion. Lines that follow this procedure include Carnival, Cunard, Holland America, Norwegian, and Princess.
NO TIPPING REQUIRED / TIPPING INCLUDED IN CRUISE FARE:
This is how some luxury (six-star) cruise lines operate. Cruise lines that follow this procedure include Silversea, Seabourn, Regent and Windstar. In general, most guidelines for tipping suggest a total of about $10-$12 per passenger per day, split between key ship staff. This breaks down to about $4.00 each for your dining room waiter and your stateroom attendant, $2.00 for your assistant waiter, and discretionary amounts for the head waiter and any other helpful staff you wish to reward. Of course, tipping is never required on any cruise, but I'm sure you'll be convinced that cruise staff are more than deserving, as they almost always provide a level of service that far surpasses all expectations!