Pre-order the expansion through Blizzard and download it before the launch.
UPDATE: Cataclysm Digital pre-orders are now available through Blizzard!
At the BlizzCon opening ceremony, President and CEO Mike Morhaime announced that players will be able to pre-order Cataclysm directly through Blizzard and download the expansion in advance of the launch. Well, Slorkuz just posted a short digital pre-sale FAQ on the European WoW forums that sheds a little more light on the process.
Players will not be able to pre-order physical copies or the Collector's edition through Blizzard. Physical boxes and the CE must be pre-ordered through retailers. If you go through Blizzard, you'll simply get a digital copy of the stand edition of the expansion.
Once you place your pre-order, you'll be eligible to begin receiving Cataclysm data when it's available. It will download in the background while you're playing, just like when you currently pre-download patches. For more details, read the full FAQ after the jump.
If you're going to pre-order Cataclysm, will you do it digitally through Blizzard or physically through a retailer?
Q. When will my credit card (or other payment method) be charged?
A. You will be charged on the day that you place your pre-order for World of Warcraft: Cataclysm.
Q. Why do I need to log in to the game once after I’ve upgraded?
A. The first time you log in after pre-ordering, your account will become eligible to begin receiving the Cataclysm data when it’s available. The data will automatically download in the background while you play World of Warcraft or while you have the Launcher window open.
Q. Can I pre-order a physical copy of Cataclysm and have it shipped?
A. Not from Blizzard Entertainment, but many retailers offer pre-orders of physical boxes and Collector’s Editions.
Q. In what regions is the Cataclysm pre-sale available? What day/time is Cataclysm launching in my region?
A. The pre-sale is available in the following regions, with realms scheduled to launch at the following times:
Americas, Australia, New Zealand, and Southeast Asia - December 7 at 12:01 a.m. PST Europe and Russia - December 7 at 12:01 a.m. CET
Q. Will a digital version of the Collector's Edition, with the exclusive pet, be available?
A. No. The World of Warcraft: Cataclysm Collector's Edition is exclusive to physical retail copies. The digital version consists of the standard edition.