I haven't seen this posted on the forum but I see it as a well known trick although a few of the people I've told didn't know it worked.
Just follow these simple steps:
- Go to Amazon, GAME, (any site offering pre-order beta access)
- Pre-Order the game
- Wait for beta key to arrive in email
- Redeem key on your account
- Cancel the Pre-Order. (Most sites don't charge for a deposit and the key still functions as normal.)
Note: I believe if you do this multiple times it can lead to an account ban on Amazon, personally I'd do it once and leave it.
If you like the game consider not cancelling your pre-order or atleast place your pre-order again. The game seems very nice and I personally like it quite a lot up to now.