Also it kind of depends on your likes and dislikes. If you are a late nite party animal, you might want to consider Carnival. If the Vegas neon glitz isn't for you, then Royal Caribbean has some beautiful ships. If you prefer a very sedate environment, maybe Holland America. Hope we have helped with your delimma.
Start with a supply of cruiseline catalogues from a local travel agent but when you are ready to shop, don't forget the web for price comparrisons. Also most of the lines have websites too.