If you’re interested in trying out Destiny before it launches and helping out in a beta to improve the game, you might want to follow the folks at Bungie on Twitter. The official account for Destiny is going to be handing out beta codes via Twitter. You can follow the account here. Make sure you’re fast on the keyboard because I’m sure these codes will be first come, first served. The codes will be at random.
Keep in mind that if you don’t want to go through the social media mess, you can always pre-order the game and get guaranteed access.