Take just one suitcase. Although many cruise lines allow you multiple suitcases, most airlines restrict the number of bags you're permitted to take with you. In addition, at some point during the trip, you'll likely have to carry all that you pack.
Pack for the season and the destination. Read about where you are traveling and the weather during your stay. Make sure that you bring clothes suited for the climate.
Mix and match items. Get the most out of the items you pack by making sure that each item can be worn with more than one other piece of clothing. Use accessories to give each combination a special look.
Include a sweater or jacket for evenings. Evenings on the deck of a cruise ship can be chilly, even in the warmest of climates. Pack a jacket or sweater and be comfortable on deck.
Stow a change of clothes in your carry-on bag. Cruise lines do an excellent job of moving hundreds of pieces of luggage in a very short time. However, it's likely that your suitcase won't be delivered to your stateroom until several hours after board the ship. Pack some casual clothes in your carry-on so you can change from your traveling clothes.