Alright, since I know people who are abusing this and skewing rankings and MMR up I'll just go ahead and leak this so Blizzard can hotfix it.
Purpose: To be leader of multiple [max: 4] arena teams under any bracket.
1. Get a lag generator. A program like Lag7.exe will work perfectly for this. Go google it or find it on this site if you don't have it.
2. Log onto WoW. Find a bracket you want multiple teams on. You can't be apart of a team on that bracket so disband/leave team. You're a newb at this exploit so you probably shouldn't leave a good team since you don't know how to use it.
3. Your lag generator will need to be set for 6-9 seconds, but it ultimately depends on your connection and how many teams you're trying to create. So set that now.
4. Open up your arena team creator so that the emblem/color/name window is up.
5. Start the lag, type in a name, hit create.
6. Because you're currently lagging, the team hasn't been created yet so the bracket is still at "Create a team" mode. Hit the emblem again on that bracket to get the create team window, go ahead and type in a name, then create the team again. If the lag ends right now, it will say you have created 2 arena teams.
7. If the lag is still going on, you can repeat this 2 more times to get a maximum of 4 arena teams under that bracket. It won't let you create anymore than that.
Aftermath: Your most recent team you created will only be seen in the UI. You can be very creative with this if you combine it with invite macros. Also, although I'm not entirely sure how it works, logging out and logging back in will rarely shuffle that arena bracket with a different team. Imagine you have created 4 teams under a bracket, team A, B, C, and D. You can have different ratings, members, and MMRs under all those teams and just need to log out a couple dozen times to shuffle between them. It doesn't matter what team is on the UI though, you can still queue for any team.