If you want to go tank heroics and raids I suggest (If nothing has changed since I stopped playing a few months ago) you get a few good blues or even epics crafted and get reputation with wyrmcrest accord for some nice starting gear. (boots chest and cloak if I remember right)
Get the Armor Plated Combat Shotgun (crafted or buy) with stamina enchant.
Get the trinket from normal Halls of Lightning.
Get the Sword from normal Halls of Lightning.
21-22k hp and uncrittable should be enough to run heroics with your guild. Less hp is possible if you have a good healer.
Your first heroics should probably be The Nexus, Utgarde Keep, Utgarde Pinnacle for epic sword and Stratholme for the shield.
Practice instances on normal mode and read up on wowwiki for heroic mode tips.
Make sure to read up on Azjol Nerub, Old Kingdom before you head there on heroic, and you will need a decent party for Halls of Lightning heroic. Halls of Stone heroic can be a pain at the little event, other than that it's cake.
Violet Hold is great for farming emblems, just read up on the bosses.
First boss in Gun Drak can be a pain, if he is still the same as pre-3.1
Oculus heroic is probably best saved for guild runs only.
This is all I can remember, good luck and most importantly have fun.
