Hello lorihope and welcome to cruise-chat;
congratulations on your first cruise; just watch out--it can become addictive. The 24th is rapidly approaching; I can almost feel your excitement.
What you can expect is a vacation unlike any other you have taken. RCCL is one of the most highly praised cruise lines.
There will be hundreds and hundreds of crew members whose sole purpose is to make sure you have a wonderful experience.
Don't worry about a thing--everything will be taken care of for you. Anything you want--just ask! Don't be bashful.
As far as packing, there are lots of good threads here and articles and lists in the cruise-reviews section; but in general, less-is-more. Don't try to anticipate every eventuality--if you forget something you can probably buy it onboard or in your first port. Keep it simple.
Once onboard, find you cabin, settle in a little, and then go explore your floating resort. Get a bite in the buffet; have a fancy drink with an umbrella and a fruit salad in it. Get into the spirit of the thing.
Find a spot on deck with a good view of whatever port you are leaving from and enjoy the sailaway.
Then get ready for your first dinner and a night of fun and music and introductions.
Have a wonderful cruise and please keep in touch.