Tanks are arguable the most important and underplayed class in the game of World of Warcraft. What are the basics of playing any of the four different tanking classes and how do you start to become a tank? Byron "Messiah" Mudry guides you through all the basics in our Big Guide to Tanking: Cataclysm Edition.
Before you become a tank you should think about it, and make sure you are doing it for the right reasons. If your main reason is getting through the random dungeon or random heroic queues instantly so that you can gear up your DPS set, you are definitely doing it for the wrong reasons. Too many players have started doing this for exactly that reason and are destroying the game for everyone else. Sure it's true that you get into an instance right away, however, you are then forcing yourself and 4 other players 2-3 hours of pain, just for your greed and incompetence.