Here's basically what you have to do:
And don't stop chain pulling until you get to a boss.
Shield slam one target, six seconds after that Shield Slam another target, six seconds later Shield Slam another target, after another six seconds Shield Slam a new target, etc. Just make sure you Shield Slam everything once. DO NOT feel that you actually have to kill off anything that you pull, that's not your job. It's the DPSer's job to kill off what you pull.
To pull a mob, target the main monster (a big brute or a spellcaster), Thunderclap first then Shield Slam the main monster. Pause for 4 seconds, to let your Thunderclap and Shield Slam finish their cooldown, then you run to the next mob and pull it. If you pull a mob, DO NOT Shield Slam every target in that mob, just the main target.
NEVER STOP PULLING until you get to a boss.
To pull an entire mob off a DPSer, you go up to the DPSer and Thunderclap. Then step away from the DPSer. Target the monster you couldn't pull off him, then Taunt and Shield Slam. Pause for 4 seconds, now go and pull the next mob.
Do not get into a Taunt war with a hunter or warlock pet, you cannot win. If a hunter or warlock pet taunts off you, then you pull even more. You want to pull so much that if the healer doesn't focus on you and you die, then the whole party will die because you pulled so much.
It is important that you stay ahead of everyone. If you queue as tank, you DO NOT have the luxury of looting corpses.
EDIT: I just looked up what abilities you have. You have Revenge, which is also good. However, its cooldown is 9 seconds so its not as readily available. But if it is available, you can use it to pull a mob. Just target the main monster of the mob, Thunderclap, then Revenge, pause for 4 seconds, then pull the next mob.
I don't use Devastate anymore, but I do remember using it a lot at your level. If I remember correctly Devastate has no cooldown, so you can always use it whenever you want. Use it while you are waiting for Thunderclap and Shield Slam to cooldown.
Edited by Beloved on 4/27/2013 4:47 AM PDT