finally started, the long awaited beta signup for StarCraft II has kicked off and it's as easy as could be to sign up, although there's one small caveat, you already need to own at least one Blizzard title to be able to sign up for the beta.
To have a chance to join the beta you also need to have a Battle.net account, although this is free. You then enter the serial number of your game(s) into your Battle.net account, download a small application that checks your system specifications and then send them off to Blizzard HQ.
The lucky beta testers will then be picked out of the pool of applicants. If you're one of the lucky beta testers, then you'll be able to download the game client from Battle.net. Those that already have beta invites from various Blizzard events need not apply this way, as they will get a beta account at some stage during the beta test, although they still need to sign up, albeit on a different website.
Not to worry if you haven't signed up, as this beta is not based on a come first basis, but rather on some Blizzard specific criteria's, so even if you're late in applying, you might still get lucky. North America, Australia, and New Zealand will be the first places where the beta kicks off with other regions to follow, although no specific date has been given as yet.
European players of World of Warcraft should also be happy to know that Blizzard will have its Battle.net integration done before the European beta kicks off, so if you can't sign up now, you will be able to do so before the StarCraft II beta starts in Europe if you only own WoW.
You can find out more details here