(1) Don't ever pay the brochure price. You never spring for the hotel rack rate, right? Cruising is the same. The list price in the catalog is there mostly to make all those promotions seem like better deals. Call a travel agent for the best deals.
(2) It's a ship, not a boat. There's plenty of nautical lingo you can ignore, but calling an ocean liner a boat will get you pegged as an ignorant landlubber every time.
(3) Wear whatever you want—until 6 p.m. It's fine to go casual to a buffet, but at any other type of restaurant, men should swap the Hawaiian shirt for a button-down and blazer, the swim trunks for slacks, and the flip-flops for business-casual shoes. Women, the equivalent.
(4) Passport, passport, passport! Many cruisers rarely leave the ship, what with all the restaurants, zip-line rides, casinos, lectures, and comedy shows. But if you ever do want to escape, one sure way to feel like a rube is to get stuck on board. To disembark at most ports, you'll need an international ID.
(5) All mandatory costs (food and lodging) are paid for up front. "It's possible to get by without spending a nickel during the trip," says Carolyn Spencer Brown, editor in chief of cruisecritic.com. But it will be a miracle if you do. Cruise lines are masterful at making all those "optionals" (spa treatments, margaritas, shore excursions) seem too enticing to pass up. So plan ahead to avoid any unpleasant surprises with the purser.
