I've only cruised once, on RCCL, November 2007. We sailed on the Mariner of the Seas out of Port Canaveral on a 7 night Eastern Caribbean cruise. I thought the ship was beautiful and huge! We were very happy with our dining room server. He was VERY funny and we enjoyed dinner immensely. The food was good and we were very lucky to have tablemates that we ended up spending much of the cruise with; 2 great couples from across the pond. We even did some island sight-seeing with them. We now exchange Christmas cards. Nice people!
I don't really drink all that much, but I had a glass of champagne one night... the cheapest glass was $18. The problem is that you don't pay for your drinks when you get them, they go on your "sea pass" (credit card). You should have seen dh and I looking at the bill on our cabin tv, trying to figure out how we could have spent so much! You don't realize how much the drinks cost, and then you start buying rounds....before you know it, your bill is $500!!! I did buy the soda card, which is a sticker they put on your sea pass so you can just get soda as much as you like. For me, it was worth the $40 or so.
We didn't do the shore excursions.... they can add up to a lot of $. We just hired a native driver to show us around. A lot cheaper, but you also risk the possibility of a problem that may prevent you from getting back to the ship on time.
My dh is a nice guy, but not real outgoing. We didn't do a lot of the "at sea day" activities. I think if I ever cruise again, I will have to go with a group of people. I think that would be a lot of fun!
I recommend watching all the cruise shows on the travel channel. They can be really informative. Also, go on websites like Cruise Critic. They have lots of reviews and tips. Keep in mind, some people will NEVER be satisfied. I'm glad I didn't listen to every bad reviewer as if it were gospel. The food on our cruise was really good. Our server and tablemates made dinner excellent!
Before I forget, I did get the motion sickness patch from my Dr. I wore them the whole time (yes, I'm a whimp). And I felt pretty much every wave, not a sick feeling, just felt it. I had to grab a rail now and then. At least it got dh to hold my hand again!
I would recommend also using a
travel agent to book it. I hear we have one on this board... Rhonda or Roz or something like that....

It makes your first time a little less itimidating. Good luck! Sorry this was so long!