We did our first cruise last year, a four day to the Bahamas. Best advice I can think of is to tour the ship thoroughly so you know about all the food, drink, and entertainment options. We ate pizza and burgers on our first afternoon, not realizing that there's a healthy food option with wraps and fruit right around the corner. Also, there are really comfy deck chairs on Deck 4, perfect for a nap or reading.
I'm sure you'll have a wonderful time. We loved it and can't wait to go again.