With nightly rates dropping to as little as $60 per person, booking an economical cruise would seem to be as simple as stuffing yourself at the onboard dinner buffet. But many cruisers, initially pulled in by low fares, end up spending far more than expected on “extras.” The following three tips can keep your cruising budget afloat…

1. Compare sellers. Though the base price for cruising won’t change that much, those travel agencies that sell a number of cruises are rewarded by the cruise lines with extra perks for their customers. Shop around and see which sellers will be willing to “gift” you with free cabin upgrades, onboard ship credits (of $100 to $200), a waiving of gratuities and more. Start with large firms such as CruisesOnly.comVacationsToGo.com…and Cruises.com.

2. Cruise on the fringe. Choose the sailings that occur on the fringes of the regular season, say, Alaska or the Mediterranean in May or September…or the Caribbean during hurricane season. That last suggestion isn’t as crazy as it sounds—the chances of being in the Caribbean during a storm are quite low.

3. Book your own excursions. On average, vacationers spend an additional 25% of the cost of the cruise once on board the ship and up to 75% more if they frequent the spa or casino! So set a budget, and stick to it. Shore excursions are the priciest onboard purchases, so book your own in advance through such companies as CruisingExcursions.com or Viator.com.