The tipping issue is pretty simple on cruises that have a "tipping included" or "no tipping required" policy.  But if someone has performed service over and above the norm, it's simple courtesy for additional gratuities to be offered.

It used to be the norm for cruise lines to provide envelopes you could to use to dispense tips. This led to a mad dash on the last days of the cruise to get a whole bunch of bills and divvy them up into the envelopes, based on suggested guidelines, and then scurry about to hand them out.

 

Most cruise lines now offer tipping options. On some lines, tips are figured out in advance and put right onto your on-board account. On other lines, you're given the option during the cruise of signing a form that allows the line to put the tips on your bill. You have the right to make changes on board, usually mid-cruise. You can raise or lower them as you see fit. If there's no option as to the amount, don't sign it. Just give what you want in the time-honored way.  Tipping policy and procedures will probably be contained in your cruise documents or in your cabin.

Stateroom steward tips are figured on a per-person basis, normally $3.50 @ day. If there's only one person, there's no need for that person to tip as much as two people in a cabin would, unless some extraordinary service has been provided. However, if there are four to a room (especially if kids are involved), the room will require extra housekeeping, and a larger tip is fair.

It is common for lines to automatically add 15% to bar bills, wine orders and spa charges. The bar add-on is fair - 15% is the basic tip ashore. An annoyance for those who drink expensive wines is having to tip more for essentially the same uncorking and pouring service as they would for less expensive wines.  Those people can change the amount. But if the sommelier decants the wine or provides better glasses, a larger tip is warranted.

 

 For spa personnel, the same logic applies: If the service is essentially the same and it's the treatment itself that is more expensive, why should you have to tip more? Tip what you feel is appropriate.

Deck personnel constantly patrol topside, looking for ways to attend to your needs. If they assist you with deck chairs and towels and free beverages, giving them a small amount is a very nice way of saying thanks. Keeping a supply of small bills on your person will facilitate such gratuities. With deck bar personnel, the tip is usually added to the price of the drink.

As for alternative restaurants, some have a tip surcharge and some don't. Surcharge tips are sometimes pooled, so extraordinary service may merit a cash supplement.

 

Besides your cabin steward, your hardest-working service persons are your dining steward and his assistant, or bus boy.  Good ones will greatly add to your cruise enjoyment.  The traditional tip is $3.50 @ day, per person, with about $1.50 for the assistant.

 

Most ships have gone to open seating in dining rooms for breakfast and lunch, with assigned tables and wait staff for dinner, only. Additionally, you may have used the upscale, alternative restaurants.  Or, you may have attended the more casual, buffet option.  It is shortsighted to only count dining room dinners you attended for calculating tips, as most of the staff rotates around all these facilities to ensure you receive top service.  In the course of the cruise, they have earned your recognition.

 

As for dining room management, headwaiters and such, it's perfectly appropriate to tip them if you've received special treatment or extra care. It's also appropriate not to tip a table captain if his only service is to introduce himself the first night and come around the last night with his hand out.  Usually, they try to be more visible and they are the ones to approach to request a special entrée or dessert for yourself or the whole table.  Just allow them at least 24 hours notice.  Permitting them to do their thing provides more enjoyment for you and a pleasant feeling when tip time rolls around.

Overall, the amount you tip is entirely up to you. If you take a moment to  realize the normally exceptional levels of service you get on board, tipping is a fair way to show that you appreciate how your vacation has benefited from that treatment. The total amount you give, factored into the vacation cost, isn't really that much, and the service staff, virtually without exception, work really hard for it. A little bit extra actually will make you feel good and encourage their efforts.