A million Americans are taking cruises every year and, unless they have been to sea before, they are experiencing a new kind of life in the tourist navy. Naturally, they have questions:

Who gets tipped? Who doesn't? How do you pick a table? What about shore excursions? What do you wear? What do you do with all that time at sea?

To begin: The porter who takes your bags from cab to check-in point belongs to the port, not the ship. He gets tipped.

Heavy baggage, if you have remembered to tag it, is sent automatically to your cabin. On smaller cruise ships a steward will take your hand luggage and show you to your cabin. If the ship has established a policy of pooling all tips, then he needn't be tipped separately. Unless it's a Russian ship, however, he will take the bill you offer. (Most vessels offer some guidance about tipping, which on short cruises comes at the end of the voyage - if necessary, ask the purser for advice. Remember that your cabin steward and dining room steward always get the lion's share.)

Don't worry about whether to tip the steward leading you to your cabin. Better to pay heed to the route he takes to get you to the stateroom. Ships are a maze of labyrinthine passageways. Aboard the Daphne recently, my room on a water-level deck could be reached only by descending to the deck above mine and then walking forward on the starboard side. Four days out of port I was still losing my way.

Tables are assigned in the first hours aboard ship. If you are gregarious and get along well with everybody, throw caution to the zephyrs and let the dining room captain seat you.(And good luck!)

If you are single and want to meet other singles tell the man. He'll oblige. If you're a family you'll probably be better off with your own table. Best of all, make up your own group and ask for a table to accommodate it.

Most cruise ships schedule a familiarization lecture given by the cruise director. He will talk about shore excursions, dress aboard ship and upcoming activities.

As with resort hotels, social rules differ among shipping lines. Some ships are extremely informal; others more proper. The Kungsholm of Flagship Cruises, Norwegian-owned and registered in Liberia, bans short in the dining room at any time and insists that jackets be worn at the table.

Tradition dictates that dress is informal the first night out and the last. Women can't get long dresses pressed the first night and by the last night the gowns are already packed. But if you're going to sea, some sort of formal dress, from black tie to the free-style evening wear in vogue in some circles, will be indicated during a voyage.

Eating is a full-time endeavor on cruise ships with six sessions of face-feeding scheduled every day: breakfast (cabin services or dining room), bouillon and crackers on deck at 11, lunch in the dining room (or on deck in balmy weather) tea and cakes at 4 and then dinner.

On the premise that no one should go to bed on an empty stomach, most ships serve a midnight supper. The late (and lamented) SS France used to ladle latenight onion soup in the fashion of the restaurants at Les Halles, the equally late, lamented Paris market.

All that caloric ingestion requires some exercise aside from tramping along on shore excursions. Besides, on longer cruises there are often several days at sea. So you may find activities like group exercise on deck, practice on a 9-hole putting green, padle tennis and swimming.

New and unusual ports are as much of an attraction as the shipboard entertainment or the flag under which the ship flies.

So many cruises come in wrapped packages, air fare included (though sometimes there's no savings), that passenger lists now represent a national cross section. New Yorkers cruise in Alaska and Californians go to Cuba.