Decide what kind of cheerleading you want to do. If you want to go to competitions, learn tumbling and stunts, and do other things like that, join all-star/competitive cheerleading. If you want something a little less challenging, cheer for your school or a football team. If you never did any kind of tumbling, cheerleading, and don't know much about it, do a recreational class for about a month and after you've got the basics down you can join an actual team.