People will predominantly be on the team the first letter of their ign places them on, unless there's a need to move some people around to compensate for balancing. Or are you referring to the 10-30Mcs, 31Mcs-BC set up?
Wait I'll be changing my ign in 5 days time though... do I select the team that my name will corrospond with or just stick to my current one?
On the initial thread go to the 10-30mcs and click the blue hyperlinked text with the appropriate team you would be assigned to due to your ign k