The best approach is a hello, nice to meet you, my name is [insert name here]. Where are you from?
Break the ice with something simple like that. It doesn't have to be complicated. The simpler the better. Where are you from works nicely because everyone on the ship comes from somewhere different. Alternatively, ask a "yes/no" question, then build into it. Like "is this your first cruise?" if yes, talk about your cruise history (if you have any) or take a minute to talk about how it is also your first.
It's not hard, and the Teen Club is a great place to start.