The first thing I do when I get onboard is find out where the maitre di is and make sure I have the seating arrangements I want. You don't always get the type of table you requested...and going to wherever he's doing his seating ASAP will ensure you get the table assignment you want.
THEN...after that, I go to see what's for lunch at the buffet and grab a bite. THEN, I go to my room and see if my luggage is there yet...if it is...I start unpacking and put everything where I want it. If it's not here yet...I'll go and explore the ship.
After that, I go back and see if my luggage is there again. (it usually is by that time)..if not..don't worry about it. You can go roaming again or take your book and sit on the balcony for a bit.
I'm not much of a drinker myself...and I'm not much of a Coca-Cola product drinker either, but what I do is....I take Crystal Light with me...usually Raspberry or Peach Tea and I use the bottled water and mix up my Crystal Light...or go down to the cafeteria and get some tea bags and make my own sun tea!
Also, being a first time cruiser...I don't know if you know if you get seasick or not. I know I get seasick at the drop of a hat...so I take a Dramamine (less drowsy) the morning of the cruise...and I make sure I take one every 24 hours...whether I think it's calm out or not. It's too late to take something once you get sick...and there's no sense having a bad time on a good cruise.
You'll find plenty of relaxing things to do on the cruise and plenty of fun things. There will be a daily program in your room when you get there and there will be one under your door every evening for the next day's events.
Relax and have fun. Any questions...email me!