Your large suitcases will arrive on board separately from you. They will be delivered to your doorstep on the first night. In the same way, you must prepare your suitcases and leave them for pick-up on the last evening. Plan to put some clothing, toiletries, etc. in smaller bags that you can use and carry with you on the last day.
On the first night, there is an evacuation lesson. Basically they show everybody where the lifeboats are and how to put on a life jacket. It lasts maybe 30 minutes, with everybody standing up on the boat deck.
You will get a daily “newspaper” in your room (the Fun Times), detailing all activities for the following 24 hours.
Drinking age is 21. The cruises I was on, we were only allowed to bring liquor on board (for consumption in our cabins) at initial departure, max 2 bottles per adult. At subsequent stops, we could have purchased more alcohol, but when coming back aboard it would be “seized” and kept for us until we left the ship on the final day.
The Carnival Victory has laundry rooms, with soap dispensers and an iron and board. Quarters are required, which you can purchase at the service desk.
For most other expenses on board, including drinks at dinner, you just present your room key/card and sign for them. A basic gratuity of about 13$ per room per night is also charged by default. Your total running bill can usually be viewed from your TV or printed from an ATM-like machine close to the service desk.
If you want Wi-Fi, it’s usually available on board for a fee. You pay for minutes of connection, in various packages. I think I paid about 50$ for 90 minutes.
One big thing they try to sell you are pictures. There are company photographers at dinner but also at every shore stop. You can view their pictures in a special gallery area, but if you want them they’re pretty expensive (and the pictures have chips, you can’t sneak them away!). Bring your camera, the (non-photographer) crew are always willing to take your picture.
When going ashore, you must have your card/key with you. When coming back aboard, you put your bags on a scanner-conveyor similar to TSA at the airport (but with friendlier people).
Expect to do some walking. Your cabin always seems to be at the other end of the ship!
You can be as entertained or as quiet as you want. I was expecting a loud, 24-hour party when I went on Carnival, and in some ways it was, but these are big ships and there are plenty of quiet spots, including the Serenity section.
Explore the ship! There’s probably something you haven’t seen yet.
Have fun!