This has been known for a little bit, but for those who don't know about it here is a little guide to get your 25% off Origin downloads. So you can get BF3 for nice and cheap.
Go the the Origin website and select register.
Enter in your email and click "start my EA Profile"
Fill out your profile information on the next page, choose a master ID, and password, but most importantly fill out your birthday for a couple days forward in time from when you register.
Also check mark "Contact me about EA's products, news, events, and promotions."
You will get an email that confirms you made your account correctly