The promised Titanfall closed beta signups are now underway on the Titanfall website, a little earlier than planned. You can register on this page, and here's what EA says about plans to test Respawn's mech shooter:

Please select the platform you would like play on for the Titanfall Beta. Completing this registration does not guarantee access into the Titanfall Beta as seats are limited. If you have been selected you will be emailed directly by EA with instructions on how to access the game no later than 11:59 PM PST on Feb 17th.

Origin Account required for PC Beta.