Do your research on each port. You may be able to see and do more on your own. For example if you visit Aruba you can easily rent a car for the day and see the entire island on your own. If you visit Puerto Limon, Costa Rica there is a ship excursion that features the canals of Costa Rica which is a very interesting tour.
Do not let problems fester. For example if you do not feel comfortable with your table mates at the first dinner or do like the location of your table see the Maitre D or Dining Room Manager and have them change you. Do not expect champagne at beer prices, that is, you will not be waited on hand and foot as RCCL is a major cruise line but not in the luxury class.
Remember, a cruise is an adventure. And try to enjoy cruising's great moments such sunsets as much as you can.
Have a great time,