Hi sailing suzie,
I'm not single, but I have been on Carnival. I don't think you'll have any problem finding other singles! There's a LOT of night life on a Carnival ship
. There should be a meeting for single and solo cruisers. Check your Capers (the newsletter, which you'll get in your cabin every evening) for the place and time.
You can also check the Meet On Board section on this site and see if your sailing is listed. If not, start a MOB yourself! You should also post your question on the Singles Board, if you haven't already.
As for what you should not do, use common sense!
I don't know if you drink, but if you do, be careful not to drink too much and don't leave your drink and come back to it. Either finish it before you dance or throw it out and get another (it's a sad fact, but people have
been known to put things in women's drinks).
If you feel uncomfortable go with your "gut". If it's really late, you might want to ask a crewmember to walk you back to your cabin. Don't go to anyone else's cabin, don't invite anyone to yours.
It's against ship's rules for a crewmember to become too "interested" in the passengers, but it does happen, so be careful.
Since this is your first cruise don't go off by yourself any further than the pier area in port. Do the ship's excursions this time.
You may already have thought of all of this, but I was just trying to imagine what I would do
I'm sure you'll have a great cruise and become a cruise addict, like the rest of us!