Here are some tips to help you enjoy your tournament:
1. Most tournaments run for two or three days, so you'll need to budget for transportation, entry fees (usually $20 or less), lodging, and meals. Tournament directors often negotiate hotel and even restaurant discounts, and you can also save some money by carpooling and/or splitting a hotel room with another player. If you don't know anyone at the tournament, just contact the tournament director and ask for help!
2. Many tournaments use three-move restriction, meaning the first three moves of the game (two for red and one for white) are drawn from a deck of 156 accepted openings. If you're used to go-as-you-please (GAYP) or freestyle openings, this can be quite a shock, since you will often have to defend weak or unbalanced positions very early.
3. If you have a tournament board and pieces (see Bob Newell's excellent article for details), bring them with you to the tournament. Unfortunately most tournaments do not enforce ACF rules about using game clocks, but it wouldn't hurt to bring one. However, if you don't have any equipment yet, don't worry-- there's almost always enough to go around!
4. You should also bring a notebook (I like using steno pads) so you can write down your games. Checkers literature uses index notation to record moves and jumps. It doesn't take long to learn, and once you get in the habit of writing down your games, you'll have a much easier time analyzing your performance.
5. Unlike in some casual games, you can't take back a move in tournament play, and if you touch a piece then legally you have to move that piece. Most players will gladly do "post-mortem" analysis after the round is over, and some will even show you exactly where you went wrong in a loss.
6. Tournaments are a great place to get advice on openings, tactics, resources, and books-- you might even go home with a couple free books!
7. Good sportsmanship will make a great first impression: turn your cell phone off when you're in the playing room, shake hands with your opponent before and after your match, do your best to keep the playing room quiet, complete all your rounds even if you're losing, and follow the tournament rules. If you run into any questions, just ask the tournament director!