If you're planning on participating in the Beta, you should keep a close eye on the Bungie Twitter feed - there are lots of useful Tweets that will keep you up to speed on all sorts of things. (Some are retweets of relevant posts from other feeds.) Examples below:
Download keys for the Destiny Beta will be emailed or found on your http://t.co/ItSr0LDMQB profile page on the start date for your console.
— Bungie Help (@BungieHelp) July 13, 2014
Beta101: Interested in streaming the #Destiny Beta to the world? Go here for information you'll need to be ready: http://t.co/aMtsRFTUeI
— Destiny The Game (@DestinyTheGame) July 13, 2014
Yep. Still working on final preparations to ready http://t.co/S2tfRP3mNB for the Destiny Beta. Hang on to those codes. We'll be back soon.
— Bungie (@Bungie) July 16, 2014