what you have to do is private message people persistently and ask them in the rudest way if you could be on their clan. Preferebly a threat against the life of a team captain if he declines you. Then, when that doesn't work, try DDoSing their clan site and filling their bulletin board with "Why won't you let me join?" posts as much as possible. If you don't have the resources to DDoS then this is your option with the bulletin board, but be a little more persistent if that is the case...create multiple user accounts and post with all of them a lot.
Once they ban your IP address, you know you are headed in the right direction. Just keep up the good fight, and they will soon relent and let you in the clan. Then say "No thanks, you suck" and move onto the next clan. Do this last part for only the first 5 clans. 5 is a lucky number.