Cruises are touted as a one-price-up-front vacation, and that's an important and legitimate selling point: Know how much it will cost before you go, pay the fare and then relax -- there won't be any unpleasant or unexpected bills afloat. But there are a few extra expenses to consider, depending in part on the requirements of the individual passenger.

The quoted price for a cruise includes a moveable feast: your stateroom; all meals (three a day with seconds and thirds, plus snacks, and almost always a midnight buffet); your ocean-liner transportation from port to port; shipboard entertainment (shows, games, movies, dancing); sea breezes and sun; sometimes even free or reduced air fare.

A good travel agent should explain what is and is not included, so the extras will not be a surprise.

TIPS: The practice of tipping is nearly as inescapable at sea as it is on land. And the question of what to tip who and when probably causes more discomfort to more cruise passengers than rough weather. Some cruise lines include information about tipping in their promotional literature, and the purser's office on any vessel will offer advice. As always, a tip is supposed to be a discretionary payment intended to reward good service. Service personnel aboard ships depend on these tips for an important percentage of their earnings in the same way as their counterparts ashore.

Basically, your cabin steward and dining-room steward are the two crew members who will give you the most service. The suggested tip for each is $2 to 2.50 a day per cabin occupant -- about double the recommendation of 10 years ago. (Some lines also recommend tipping the busboy $1 a day per person.) On short cruises, tips can be given at the end of the journey; on longer trips, give them about once a week.

Other personnel you may deal with are the maitre d' (tip for special attention as in any first-class dining room) and the wine steward, bartenders and deck stewards (about 15 percent each when service is rendered).

Never tip officers or staff.

Holland America Westours instituted a "no tipping required" policy aboard its Netherlands Antilles-registered vessels in 1972. Some passengers undoubtedly still feel the need to tip individually or perhaps as part of a dining-table pool.

Greek maritime regulations require crew members to pool gratuities; so instead of handing out individual tips (they cannot even be added when you sign bar chits), passengers on Greek ships are advised to set aside $6 to $8 per cabin occupant per day and leave it at the indicated office at the end of the cruise.

PERSONAL EXPENSES: Liquor is not served free, but it will be somewhat cheaper afloat because it's not subject to the same duties as in the United States. (Beer, wine and mixed drinks on board might range from $1.25 to $2.)

Gambling casinos are now operating on a number of cruise vessels. If you intend to challenge the "house," bring additional cash you can afford to lose.

Laundry, beauty-shop services, massages, ship-to-shore telephone and telegraph cost extra. So do flowers, if there's a florist on board.

Shopping, both in the "duty-free" gift shops aboard (open when the vessel is at sea) and at stores in various ports, often offers bargains. The price tags reflect varying degrees of tax exemption allowed the importers by their government because the goods are not intended for use within the country of sale. But it is wise to price items you are interested in while at home so you will have a reference point in other countries. Remember that you still will be required to pay duty to the U.S. Customs Service if you exceed your U.S. resident exemption ($400 per person, in most places). You might want to check the latest rules on import charges with Customs before embarking.

Illness requiring medical attention will be treated by the ship's doctor for a reasonable fee.

Shore excursions are sold by the cruise lines, which will make certain you are aware of their packages before the vessel docks at the first port of call. Or you may find you can make your own sightseeing arrangements for less after leaving the ship.

But listen carefully when officials tell you the time your liner will up anchor. They will definitely sail without you if you return late from a private tour -- and then you'll have to fly to the next port to get back on board.

And that could really upset your budget.