First you will need to have a warrior level 70. The best warrior for horde is Tauren, for alliance is Human. So untill you get your warrior to lvl 70 you should build up your talents in arms and fury. When you are 70 just go to warrior trainer and unlearn your talents. Then use your talent points like this:
And when you tank you will need to change stances almost all the time. So you will need a good shield, high dodge rating, and armour that increases your defense stats. Don't worry about the weapon...you don't need it. You have "DPS" players to do the killing.