In order to access the limited edition you must pre-order your copy before January 11^th 2011. The BioWare Signature Edition includes:

Also if you head over here you can check Penny-arcades latest Motion Comic and register to get an exclusive Penny-Arcade in-game item. The Hindsight Belt can only be obtained by logging in with your EA account and registering for the Dragon Age II Newsletter. We just got the Staff of Parthalan not too long ago, so who knows what else will be in store for us in the coming months

So if you were a fan of the original Dragon Age and really want to make sure you get your money's worth, I recommend you get out and pre-order your copy before January. Also sign up for the newsletter and watch the official site on a regular basis because you're not going to want to miss out on any more of the free DLC!