My Cruise tips:
1. Review the actual ship before you book the cruise. Older, smaller ships are not nearly as fun. Use CruiseCritic.com as a source.
2. If you are under 50 years old, do not cruise on Norwegian (NCL).
3. Get off the ship at every port. You will be bored with the ship after a few days at sea anyway.
4. Book your excursions on shore, not through your cruise line. (If you are a risk taker) The ones through the cruise line are guaranteed to get you back to the ship in time, but they cost more and are more boring and safe. We found the ones not through the cruise line were cheaper, more fun, less people, and not as commercialized.
5. We loved pretty much everything about Royal Caribbean and hated almost everything about Norwegian. You chose well with R.C.
6. You typically have 2 "formal" dinner nights on a 7 day cruise. You do not HAVE to go to them though. You can go to one of the other restaurants those nights if you want to. We really enjoyed the formal nights though. Unless you are an antisocial person, you will probably enjoy dressing up and eating with other couples.
7. Watch your bar tab if you drink. It is not uncommon to rack up a $500 bar tab if you drink moderately. A couple that went with us had a $2,000 bar tab at the end, because they buy drinks for everyone. Of course, they are seasoned cruisers with money to blow, so its no big deal to them.
8. Pack liquor in your CHECKED LUGGAGE. We have done this twice, and have received our liquor both times. Drinking a few mixed drinks in your cabin, or in your drink container is MUCH MUCH cheaper than buying it from them. Mixed drinks are ~$8 each. They have warnings that say if you do this, they can kick you off... but they won't. They want you to spend money on board. The worst that happens is they confiscate your liquor. Read more on CruiseCritic's forums. Also, if you buy liquor on shore, they confiscate it until the last day and deliver it to your room.