Instructions
Obtain an authenticator. You can purchase a physical authenticator in the Blizzard store or download the mobile authenticator app on your smartphone. This provides an additional field after logging in where you must input numbers displayed by the authenticator.
Create a secure password that cannot easily be guessed. Use capital letters, lowercase letters and numbers jumbled together. Do not use words involving your favorite foods or bands or anything else personal.
Do not respond to fishy emails. While Blizzard may email you from time to time, their employees will never ask you for your password. If you receive an email from someone claiming to be from Blizzard asking for your password, even if the email address appears to be authentic, do not respond.
Enter your password only through your Battle.net game or the Battle.net website. If the website does not begin with "x.battle.net," where "X" represents your country, the website is not authentic and you should not enter your information anywhere on it.
Do not log in on public computers without an authenticator. The computer could have keylogging software that records what you type in and whoever has access to the software can read what "World of Warcraft" login information.