Cruising: Most ships offer a choice of two sittings for evening dining. However, never assume, even if you have reserved a seat in advance, that everything has been arranged.

A friend of ours telephoned the other day to grouse about writers heaping praise on cruise lines that offer single-sitting meals.

Most cruise ships offer two meal sittings because their dining rooms are too small to seat all the passengers at the same time. The first-sitting dinner usually begins at 6 or 6:30 p.m., with the late or second sitting starting at 8 or 8:30 p.m.

Some lines, such as Princess Cruises, give you the opportunity to choose your sitting, table size and smoking or nonsmoking areas in advance by mail. On other lines you must make your reservations with the maitre d’hotel as soon as possible after boarding.

When entering your cabin for the first time, check for an envelope or card that specifies a table number and meal sitting. If there isn’t one, someone from your party should check in the dining room where a reservations table is usually set up. Never assume, even if you have specified everything in advance, that everything has been arranged.

Is it better to eat first or second sitting?

Take into consideration your mealtime patterns. Generally, the earlier time is preferred by older passengers, particularly women traveling alone or with friends of a similar age, by families with young children and by most passengers on scenic, early-to-bed, early-to-rise sailings.

The late sitting usually attracts young and middle-aged couples, singles looking to meet other singles and the majority of passengers on Caribbean and “party� cruises. Where itineraries feature frequent ports of call and late-afternoon sailings, passengers eager to spend more time ashore try to arrange second-sitting dinners, as do those passengers who prefer an extended cocktail hour.

On a single-sitting ship, dinner usually begins about 7:30 p.m., but there is less pressure for the passenger to be prompt. As on two-sitting ships, tables are assigned for all dinners (and on many ships for breakfast and lunch as well). You’ll find single-meal sittings on Royal Viking Line, Clipper Cruises and Cunard Line’s Sagafjord and Vistafjord.

Also, a third system is becoming popular with passengers who dislike the regimentation of assigned times and tables. Several small and luxurious ships operate much like restaurants, notably those of Cunard Sea Goddess, Seabourn Cruise Line, Windstar Sail Cruises and Oceanic Cruises, as well as the expedition ships of Society Expeditions and Special Expeditions.

Passengers can arrive for dinner when they wish, within a specified time frame, and can sit where and with whom they please.

Although this works on small ships, it could become chaotic on larger vessels. Don’t expect a megaship such as Royal Caribbean Cruise Line’s Sovereign of the Seas to encourage its 2,600 passengers to drop in for dinner any time and sit anywhere.

There are several advantages to having a table assignment on a large ship. You can meet fellow passengers at the beginning of the cruise, you get your own waiter who quickly learns your food and service preferences and you may get the same sense of belonging that a favorite restaurant on shore offers.

Although you can get a table for two, a table for six or eight may be preferable, particularly if you don’t want to be alone. Singles should request the largest table possible, preferably with other singles.

If you find after the first dinner that you don’t like your table companions or waiter, go to the maitre d’hotel immediately and request a change. You may have to change your sitting, however, if all the tables are full.

On the yacht-size American-flag ships of Clipper Cruises, passengers dine where they wish the first couple of days until they get to know each other, then they choose their table size and dining companions.

Sometimes the dining room is designated as “open seating,� which means you will be seated in the next available space.

A few new ships, notably the Royal Viking Sun and Norwegian Cruise Line’s Seaward, also operate a restaurant, an elegant alternative dining room where the passenger can make a reservation and pay a set price for dinner, about $30 per person on the Seaward, $45 on the Royal Viking Sun.

If you’re on a special diet such as low-fat or low-salt cuisine, you or your travel agent should inform the cruise line in writing as far in advance as possible. It’s a good idea to remind the maitre d’hotel again on the first day.

Except on those lines that do not require tips--Holland America Line, Windstar Sail Cruises, Cunard Sea Goddess, Oceanic Cruises, Seabourn Cruise Line and Society Expeditions--you will be expected to tip your waiter and bus boy or second waiter (usually $3 a day for waiters, $1.50 a day for bus boys) at the end of the cruise. If it’s a long cruise, plan to tip them at the end of each week or two weeks.

Wine stewards and bar waiters should be tipped when the bill is presented. If you have requested special meals or dishes from the captain or maitre d’hotel, he too should be tipped at the end of the cruise.