There is a great cruise forum out there that I cannot remember the name of at the moment but someone will probably come along with it.
The only thing that really stands out in my mind is, the day you disembark can be a long one. They go by plane tickets, cabins, etc. in priority so if you have a later plane and are in a regular cabin you will probably not disembark until late in the day. The only problem is you have to be out of your room fairly early. It can get pretty boring waiting around all day to leave!
i found this site to be very helpful: http://www.cruisecritic.com/
they have a helpful board too. i did a lot of research to figure out what to do on each island. i didn't do any of the cruise sponsored ones, they cost more and you get less time doing stuff on the island.
cruisecritic.com is what i use to talk to people who are going on the same cruise as me. Go to the roll call section.
I've been on 6 cruises so far and I love it! It's so much fun. I love watching the sunrise early in the morning. There are many activities and shows. Most ships have like a store or 2 that sells necessities and souvenirs. I usually arrive at the ship as early as possible. The ships i've been on usually departs around 4 or 5. But I go usually around noon, get some lunch as the buffet, roam around the ship, and take a dip in the pool. Make sure you keep a bathing suit with you because sometimes you won't get your bags/luggage till after dinner. Keep your necessities with you.
I usually book my excursions through the cruise line even though its more expensive because its more convenient. You won't have to worry about missing the ship because its set up through the cruise line.
Don't be afraid to think outside the box when it comes to excursions either. One of the best ones we had was when some random taxi driver (we all still remember his name and this was almost 20 years ago) took us on a tour around the island of Antigua. It was completely random and he I think he just approached my Dad as we got to the end of the dock and it ended up great. Be careful obviously but don't assume you already know all of your options before you get off the ship.
I love cruises! I have a short one booked later this month and I can't wait to start planning my next "real" one. Cruise Critic has lots of information so be sure to check out all the different forums and sub-forums.
It's fun but we got tired of the noisy kids and food. I am just glad we had a port everyday or else we would have gone crazy on the boat. I think next time I would get a bigger room and upgrade to a nicer cruiseline.