It's time to book a cruise if cool ocean breezes are calling your name and you're dreaming of lounging poolside, 24-hour buffets and enchanting ports of call.

More than 20 million people worldwide are expected to embark on cruises this year, according to Cruise Market Watch. The Caribbean tops the list of the five most popular destinations, followed by Europe, Alaska, Bermuda and Hawaii.

Planning a cruise, however, is usually not something to do last minute. Most vacationers book a minimum of six to nine months out and it's not uncommon to put a deposit down one or two years out. However, because cruise liners like full ships, it's sometimes possible to find good deals at the last minute.

BBB recommends keeping the following tips in mind when booking your next cruise:

If you're new to cruising, consider working with a trustworthy travel agent who is knowledgeable about different cruise lines, ships and destinations. You can find reliable travel agents and check their BBB Business Reviews at bbb.org.

Know your budget and stick to it. Base prices may appear affordable, but the total swells when airfare, excursions, shopping, spa treatments, entertainment, gambling, upgraded dining, tips, etc., are factored in.

Consider the time of year. Check out what the weather is typically like at that time of year you want to book your cruise. Temperature, hurricanes and rainy seasons can make a particular destination less appealing.

Know where you're willing to compromise. You may be dreaming of a stateroom with a balcony, but an interior stateroom might be more in line with your budget. If you take advantage of the ship's offerings and amenities, you won't be spending much time in your room anyway.

Shoulder season - when most folks stay home - often comes with modest savings, such as 10 percent off typical high-season rates. If you're looking at a Caribbean cruise, for example, shoulder season is September and October, the non-holiday weeks in December, and early January to Presidents Day.

Ask for a discount. If you're a return customer, mention this when booking and ask if you are eligible for a discount. A third or fourth person in your group could get a 30 to 60 percent discount. And those 55 or older and active and retired service members should always inquire about discounts.

For more consumer tips and information, visit bbb.org.