Hello Linda,
I would advise finding a local travel agent that specializes in cruises. Even ask someone that has been on cruises for the name of their agent. As far as choosing a cabin, it depends on what you want, and how much you want to spend. We prefer a balcony cabin on an upper deck. My wife and I have been on over 30 cruises, so we've tried different cabins and locations. For a first time cruise it doesn't matter because your not spoiled yet.
