Depends on where you are. I'm in western australia and we got rules for pony club and EWA, 2 organisations with different rules. Pony club has more stupid rules to poke a stick at where as EWA is more at your own risk.
So depends on where you live. Go to local events and ask people. Most rules are pretty easy ones that might be the same for showjumping. Well at least you know you can jump :)