National Geographic Sea Bird in Alaska
Photo: National Geographic Sea Bird in Alaska / Lindblad Expeditions

5. Book during a promotion.

Cruise lines run promotions several times a year, so be ready to pounce on deals during holidays like Black Friday, Memorial Day, and Labor Day. Here's a good strategy: Make an early booking to get the best available price, then monitor your sailing for price drops and special promotions that pop up. Be prepared to cancel your sailing (within the allowable period) and rebook with the new, better deal. You can work with a travel agent who specializes in cruises to do this, and they in turn may score onboard credits for you.