Changes

Only if you are already on the Blizzard's friends list. They do keep a list of good testers from past games, and add people to it when they reliably report numerous bugs, but the names on this list are kept private.

Aside from marrying a Blizzard employee or becoming one yourself, you could try attending BlizzCon or other such conventions, since they've been giving out cards good for future beta test slots at such events. Admins of popular fansites and employees of major gaming info sites usually get beta slots as well; sometimes they even have extras to give out to site regulars. There's no way to increase your odds of being chosen from the public sign up period though, since the criteria Blizzard uses to pick such people varies, and is largely random.

==How long after the sign up period will those selected be notified?==