Key's were given to us via the magazine's we bought several month's ago. These key's were submitted to our sony accounts as priority key's.
Supposedly tomorrow, an email will be in your box, giving you access to planetside 2 beta, if you have submitted your priority code.
I've heard nothing more at this stage.
If you still haven't got a beta code, I suggest checking Planetside 2's twitter feed as they give away codes regularly.