Are there any specific areas or subjects for which you're looking for tips? There are several folks on here who have or still do work on ships and will be more than happy to help.
I would say one of the biggest tips is to not be surprised by all of the "extra" stuff you will be required to do. I am not sure about Carnival specifically but in general you will be part of emergency drills, lifeboat teams, you'll have a lot of the corporate training to go through (ethics, sexual harassment, don't hook up with passengers, etc...), and there will be a lot of other events scheduled in your performance spaces (bingo, shopping lectures, karaoke [vomit], etc...). Just remember that you are one part of a large floating hotel and the ship's operation does not revolve around performances. That is the biggest difference from traditional land based theaters.
Safe travels and happy sailing.