How To Sign Up for Diablo III Beta
1. Go to Battle.net
2. In the upper right, either Log In to your existing account or Create a New Account.
3. In the upper right, click on "Account".
4. On the right, under the green button that says Add a Game, click "Beta Profile Settings".
5. Download and run the Beta Opt-In Application.
6. Under "Beta Test I'm Interested In", choose the universes that you are interested in, including Diablo Universe (for the Diablo III beta).
7. Click "Update Preferences".