Rodeos are a lot of fun, and you'll meet a lot of lifetime friends.
Make sure you take the time to practice at home. The rodeo itself is not the time to practice; it's the time to perform. Also, make sure that your horse is going to be able to handle the sights and sounds of a rodeo, as many things (loud music, banners on the fence, etc) can be scary for an inexperienced rodeo horse.
For barrels, check out our barrel sticky on the barrel racing forum. Barrel Racing Exercises and Drills.
I myself am not a roper, so I can't give you too many tips on breakaway.
Ribbon roping? I've actually never even heard of that, and its not a typical "rodeo" event.
Main thing --> Well before it is your turn to go, make a game plan in your head. Imagine a perfect run in your head. Think about every move you need to make, and every cue you need to give your horse. Hold onto that thought, and then go do it when its your turn. Do not pay attention to what others are doing. It doesn't matter how they warm up their horse, or how they run their horse, etc, because you are not them. You are you. Stick to your game plan. Don't be influenced by others. It's easy to get caught up in the moment and think you have to do what everyone else is doing.