At the end of each week, your Team Rating is used to calculate how many Arena Points your team will receive for this week. Your team needs to have fought a minimum of ten matches per week to be rewarded with Arena Points, and a player must have been in at least 30% of all your matches to be eligible for that week's points. It is important to note that the points you receive in a given week is determined by only one team, and not from a combination of all your teams. Whichever team you are a member of that would receive the most points after accounting for Team Rating and team type becomes the sole source for your points for that week.

^ copied from...
http://www.worldofwarcraft.com/pvp/arena/index.xml