I've never read a &quot;How To&quot; guide for tanking or pvp, so if I write something that's crap, sorry, it may turn out I don't really know what I'm doing. 

Tanking, to me, is about keeping as many monsters on you as safely feasible, mitigating as much of the incoming damage you can, keeping a decent threat build rate up for dps to do their thing, and being aware of what every monster you're fighitng is doing and capable of. 

Warriors tanking have to be able to keep that threat rate up, racing the dps, and at the same time hopefully have a space cushion to spare some rage for shield block to take full advantage of our special tanking trait.

My spec includes 5 points in the arms talent of parry, as well as 3 in improved thunderclap. Once thunderclap became usable in defensive stance, it became an ability I really rely heavily on, and the improved version of it is extremely helpful. When I start off a pull, the first thing I try to do is thunderclap (Hopefully I can sneak it in there before CC lets their sheeps and shackles fly). This gives you a good burst of initial threat, and helps to insure that when those CC effects break, the creature has some attention for you. Next, you start stacking the sunders on your target. I keep my heroic strike and sunder armor keys close together along with shield block. It's a quick rotation between the three, and then devestate takes the place of sunder armor, alternating it with shield block and heroic strike. If rage is available, I'll use shield slam. The placement of the hotkeys is pretty essential. 

Sunder armor, heroic strike, devestate, Shield slam, shield bash, and thunderclap and shield block are my most used keys. 

I say this, because I often used to place my hotkeys badly, keeping important abilities too far away from one another so that my weaving of them is clumsy.

Next thing about tanking is being aware of the best position in the area to fight. When you approach a pull, and see what you're up against, first thing you do is find a place to lure them to you. The place you choose should be safely away from any proximity to roamers, but it also is in such a proximity that no effects like fear can endanger a party member and fling them into another stationary group.

Intervene: This is an ability that I am only just now starting to try to implement into my playing. There's a macro you can use to cause it to automatically target a member who's under attack by your target, making the use of it quick and efficient. I avoided it because I was too slow to get the target in danger right, or I'd be at the wrong range from my intervene target and it would get all screwy. Intervene helps a ton on fights where you know something soft is bound to get hit by something, and if enough warriors do it, you're mitigating a good deal of damage. An example of an encounter where intervene may be a life safer is the Big Bad Wolf event in Karazhan.

That's all I got, forgive me if I just stated the obvious! I'm interested to read about some other classes. I'm not going to bother posting about playing an elemental shaman, we shoot you with laser beams and try to kite you if you chase us. The threat we produce is ridiculous and if we don't crit enough we're way out of mana soon. :)