Update: And that just happened, all character services are now 50% off in the US.
So if you're looking to try out a new home, a new race, a new look, a new name, or a new enemy, now's the time to get involved. It's really easy to do, just head over to battle.net, log in, and you'll be presented with your accounts, head through to the right one, select the service you require and you will see if your character is eligible. From personal, and very recent (darn it) experience, if you're looking to realm transfer you'll also need to empty your mailbox and make sure you're not in charge of any arena teams. Either that, or log in and out an awful lot!
What's more, it messes with your addons quite a bit, as the profile your character's using will reflect its new home. The same will happen with name changes, so ensure that you have addons with profiles wherever possible to avoid yourself a lot of reconfiguration. Enjoy your new perspective!