You need a racing license and there are a lot of equipment rules. Go to a race and talk to the riders, usually the pits are open after the race and as a rule flat track racers are a good bunch and love to talk. There are several sanctioning bodies in Canada, I don't know about the USA but the AMA would be a good place to check for classes and rules. You start in whatever displacement class you pick as a novice, every year the best riders from novice class move up to intermediate and so on to expert. Intermediate is fairly serious and the expert class requires a lot of dedication and money.
There's also Speedway which is for certified lunatics only.
