You won't have to max out your credit card. Most cruise lines, including Carnival Cruise Line, Norwegian Cruise Line, and Royal Caribbean International, require only a deposit when you book, and the amount varies depending on the length of your cruise. For example, on Norwegian, a deposit for a two- to six-night cruise in a standard cabin is $100 per person. On Carnival, the required deposit is $100 per person for a three-night cruise, with the amount increasing for longer cruises. The deposit amount can vary according to the itinerary as well. Deposits for Alaska cruises on Carnival, for example, are $400 per person.

Once you’ve made your deposit, you have anywhere from 60 to 90 days before your cruise to pay the remaining balance. The exact date varies from line to line and depends on the length of your cruise, so be sure to check the fine print. For Norwegian, final payment is due 75 days before a two- to six-night cruise, and 90 days before a longer sailing. On Royal Caribbean, final payment is due 60 days before a three- to five-night cruise and 75 days before a cruise of seven nights or longer. On Carnival, you have until 60 days before your three-night cruise or 75 days before longer sailings.

None of the major lines have official payment plan setups, but you do have the option to make multiple payments in any amount you want, whenever you want, after the deposit — as long as the balance is in before the final payment deadline. It's smart to establish your own goals for paying in increments, so the final sum doesn’t creep up on you.

If you're planning on taking a Disney cruise, the family-friendly line's Disney Vacation Account works as a virtual piggy bank where you can put money aside for a future trip.

Just as with flights, cruise fares fluctuate as the date of the sailing approaches. If you find a lower price for your sailing for the same cabin category, most major lines, including Carnival, Royal Caribbean, and Norwegian, will honor the lower price even if you've already booked your cruise. All you have to do is fill out a price protection claim (sometimes called a best price guarantee form) or make a call to your booking agent. The difference in price is put into your account in the form of onboard credit, which you can use for things like wine with dinner, massages at the spa, and cocktails by the pool.

Some cruisers use this booking strategy to their advantage, booking way in advance and keeping a very diligent eye on sales — raking in the credit each time they find a lower price (which could be several times before the final payment is due).