This comes from - http://bf3blog.com/
The Battlefield 3 beta is set to kick of tomorrow for those with early access, and on September 29 for everyone else. We’ve spoken to an EA representative, and gotten confirmation on a few things, mainly, how to get the beta, and when it begins.
How to access the beta
EA will send out emails with beta codes and a link to where you can redeem the code and download the beta.
The emails will be sent out to those who pre-orderd on Origin (to your Origin email account). Emails will also be sent out to Medal Of Honor users to their EA master account emails.
Steam owners of Medal of Honor will receive the beta code in their MoH Steam page, under “CD Keys”.
Emails will be sent out later today/tonight.
Xbox 360 and PlayStation 3 owners will get mails sent to the email address they used for their pre-order.
MoH owners will receive the email to the address they used to sign up for the early beta (redeemed your Online Pass).
The beta is estimated at 2.6 GB.
Beta start times
For those with early access, the beta starts on September 27 at these times:
5 AM US Pacific
8 AM US Eastern
2 PM Central Europe (14:00)
10 PM AEST (Australia)
9 PM JST (Japan)
For everyone else, the Beta starts on September 29 and access should happen on the same times as listed above.
Once you receive your beta key, you can redeem it on this website.