Different cruise lines and ships detail this method. Traditional Tipping - you are given premarked envelopes in your cabin the last day of the cruise. You inset the amount for each named individual and hand that envelope to them personally on the last evening of the cruise. Automatic Gratuity charge to your Sign & Sail (Celebrity, Princess & Carnival), you can leave the charge on your account and each person - waiter, assistant waiter and cabin steward will be automatically given the suggested amount. If you wish to change this charge: remove it, increase it, decrease it, you may go to the Pursor's desk at anytime during your cruise to make changes and you may also give cash in envelopes that are availabel at the Pursor's desk. If the maitre de has done something special for you, then certainly extend a gratuity, if a child care provider has taken special care of your child, a tip is welcomed, etc. Bar drinks, wine and soda/bottled water purchases include the 15% gratuity automatically. If there is a Sommalier on board who assists you with wine purchases, he too could be extended an additional gratuity.
Some lines give you the best of both worlds. You take a form to the purser indicating how much you want to tip whom, which is charged to your tab. You are given cards indicating the name of the tippee and amount which fit in the forementioned envelopes and give you the opportunity to look the server in the eye when you present him/her/? (in some cases) with a gratuity.