Will try to make it as short and simple as possible ) without going into skills. Further guard guides will come when/if I get enough practice with the new skills /trees.
Your role as a tank is to take all/most of the damage from your fellowship, you are indeed the meat shield! Using your skills and threat your role is to grab all mobs in a smart way, not enough to just go in and grab them randomly, have to actually use your head :P Bells of Dale first boss is a good example, lots of adds and while you should grab most of the melee adds, grabbing the archers should be left for the champs, cappies or ranged dps, if you move the boss around too much he will damage/one shot your fellows.
Then there's positioning, always try to turn mobs from your fellows, make them face you leaving their backs to your fellows, doesn't mather if the mobs do aoe or not, always do it! This way you can always see what's going on with your fellow, if someone pulled a mob or if a patrol mob is coming and of course mobs cant block while on their back.
And once you got all the mobs on you please don't move around... Nothing more annoying for a champ than have to constantly chase the mobs cause the tank can't stand still -.- also try to make the mobs do kind of semi circle around you, aoe classes will love you for that ;)
Last but not least: learn to work with other tanks, in a raid when normally there's 2 tanks if the other tank is doing fine then do not try to grab mobs from him, seen way too many times tanks doing this and causing a wipe cause suddenly mobs turn other way, start smacking other tank and healer wasn't prepared for that sudden change...
