Blizzard’s paid character transfer has begun. If you wish to transfer to another realm, you can do so for $25 and move to and from one of the main 5 servers; Altar of Storms, Argent Dawn, Demon Soul, Illidan, and Warsong. Blizzard has a short FAQ on the official site, should you be confused. More realms will be added later, Blizzard says.

We’ll gradually scale up the list of realms to accommodate more players as quickly as possible. To start transferring your characters, just log in to the account-management section and click the Paid Character Transfer button. Good luck in your continued adventures in Azeroth, and have fun on your new realm!

Read (Blizzard.com)

Transfer FAQ (Blizzard.com)