World of Warcraft account and make a couple clicks and bang, you're done. Do be warned that you'll only get an email if you're actually accepted into the WotLK beta and not a simple confirmation email for entering.
We can't imagine that it'll be very long before the beta actually starts now that Blizzard is accepting both EU and US entries. Once the beta does begin information about what we can expect from World of Warcraft's next expansion should begin to flow even more freely. It's possible that we'll see the beta begin before Blizzcon 08, so make sure to get your submissions in fast, while the clickin's still good!