The biggest cruise lines in the world boast expansive fleets with many different ships to choose from. You'll likely find smaller and mid-sized ships that cater more to adults, as well as large ships that are loaded with attractions for all ages. These ships usually cover a wide range of price points, too. For example, sailings on older ships typically cost less than on the newest ships in the fleet.

Deciding which ship you and your crew will be most comfortable on depends on a variety of factors, including how many people you're traveling with, how many connecting rooms you'll need, whether this is an adults-only getaway and how much time you plan to spend on the ship versus on land. For example, if you're eyeing itineraries with lots of sea days, you'll want to consider a ship that offers plenty to do onboard. If you and your friends are foodies, research the dining scenes on different ships beforehand to see which ones appeal most to you. Looking to spend the least amount of money? Look into older ships: Many of them sail to the same popular destinations as their larger, more expensive sisters. Personally, I prefer the more intimate vibe of a smaller ship when I'm traveling with a group of girlfriends and the energy of a bigger ship when there are kids in tow.

Working together as a group to decide on how you're traveling together can help make the trip smooth once you arrive.

For example, when I'm traveling with a group of adults, I always purchase a beverage package because it helps to save money and simplify the planning process. Royal Caribbean's® deluxe beverage package, for example, covers unlimited alcoholic beverages during your entire sailing for one flat price. And if you're traveling with foodies, consider buying a specialty dining package — either for three nights or every night of a longer sailing. These value-boosting bundles allow you and your friends to taste your way across the ship's specialty restaurants at a deep discount. You can dine at, say, a Tuscan spot one night, sushi the next night and then a steakhouse on the following night ... and you can make your dinner reservations before you even board the ship in the cruise line's app. Another activity to book in advance: Tickets to evening performances, such as Broadway at Sea℠, comedy shows and aerial acrobatics performances in the AquaTheater are available 30 days in advance in the app.

On girls weekend getaways with my besties, I also like to plan in advance for a spa day onboard whatever cruise ship we're sailing. I highly suggest booking spa treatments before sailing via the cruise line's app or website, as it's usually cheaper than purchasing them onboard the ship. The most popular times are sea days, and you'll need to plan ahead to get those appointments — even spa day passes (which provide access to the steam rooms and saunas as well as other treats like heated, tiled lounge chairs) can sell out in advance. Consider also booking manicures and pedicures for your group for the first day, and blowouts in the salon for formal night. Another nice girls or guys weekend trip ideas: working out together. Onboard, you'll find group fitness classes, such as yoga and pilates, and you can also book a group session with a trainer.

If our sailing involves stops at destinations we've never visited before, my friends and I also purchase shore excursions in advance so that we can get to know each port with an expert guide, and factor in the expense to our planning. Every destination usually includes a wide range of excursions to choose from at different activity levels and price points, from cooking classes to catamaran sailings to zip line adventures and city tours. Your group can work together to figure out which options are best for the whole gang, and book them before they sell out.