The unfortunate upshot to all this is that it can be hard to get into the instances where the gear you need drops, if you're not geared enough to tank them yet. There are a few quest drops and crafted items that can help close the gap, but the catch 22 factor still exists. To get the gear to run the 25 man raids, you need to run the 10 mans. To get the gear for the 10 mans, you should be doing heroics first. If you want to survive inside the heroics, you need to run the normal level 70 instances first. To a degree you can fill some of these holes with Badges of Justice, but you need to get your gear up high enough to get those first, which requires at least a solid set of gear.
Part of the problem is that a tank's gear more quickly shows its weaknesses than a DPSer, much as a healer's can: if you're an undergeared DPS player on a run where everyone else meets or even exceeds the gear requirements, then it probably won't matter much. After all, even undergeared you'll still be contributing damage, and usually gear won't hurt your CC one way or another if you're providing that. But if yoy go into heroic Slave Pens in a set of level 66 'Of The Champion' plate and expect to tank it, you're going to die unless your healer is simply awesome, and even then said healer is going to remember this run as a nightmare where he or she couldn't take their eyes off of you for a second. Some of the DPS will figure out why they died to damage that normally they'd get a cheap spot heal for, as well, if somehow that healer manages to keep you up.
It would be nice if all up and coming tanks could come to the 70 instances in solid tanking gear already, but since leveling in the game often requires you to do a lot of questing and grinding, pursuits that aren't as tank friendly at least as far as protection spec warriors are concerned, a lot of warriors spec arms/fury or fury/arms for leveling and as such end up collecting a lot less tanking gear. (My advice? Hold on to every single quest reward you get with good tanking stats until you get another piece with superior stats. My human warrior uses a green ring that he gathered in this fashion to tank heroics, it's a surprisingly strong ring considering.) Don't always confuse 'good' with 'blue or purple' either. You can tank level 70 instances, even heroics, in greens if they are the right greens. This is not to say you can do it in off the rack AH purchases, you'll need to put some effort into looking over your quest rewards, comparing their stats and deciding if you have anything as good. The Wind Trader's Band I linked above is a good example of a green that will last you quite a long time.
Another thing to consider for the up and coming tank is that tanking is more than just stamina and defense. These are important stats, yes. You want to survive, and you want to mitigate incoming damage. But new stats like expertise are much more important than they first appear. Expertise is shaping up to be a very important tanking stat. Not only does it help you generate aggro by ensuring you are dodged less and parried less, but there's a hidden advantage to having higher expertise: it is a mitigation stat.
Higher expertise means that you are dodged and parried less, which against a boss reduces the chance he will get a counterattack move against you, which is similar to the usual attack he or she can do but happens faster than normal, making it hard for a tank to have a shield block or other avoidance move up to smooth it out. Since it can be hard to tell if you've just been dodged or parried, a stat that reduces the chances of this happening also reduces the chances for a surprise big hit or crushing blow in response to you being dodged or parried.
So we have a natural gear progression to consider, and we know that we need to improve our tanking stats across the board as best we can (you'll be capping defense at 490 first, since it's vitally important to prevent crits, and then working on your other stats), getting your stamina up, your expertise, hit, dodge, block and parry as gear with those options becomes available to you. You'll also be making sure that you have all the proper buff foods and consumables, as they can help push you higher on any places you might be lacking to help provide some more slack for your healers. So what else do we need to do to tank bosses?
Figure out what it is they do. Sometimes, this may require some wiping.
Nobody likes to wipe. Especially not the dudes in plate! Believe me, everyone, if the warriors (and paladins for that matter) had it in their power, your groups would never, ever wipe. We hate repair costs the way other folks hate overripe bananas. (What? They're nasty.) I heartily recommend to any and all tanks that you go out there and read up on a new boss as soon as you can, and try and get the rest of your group to do so as well. And once you've done so, make sure to cover the boss in detail for any new players in your group who may not know the fight. But sometimes, if you're unlucky or just very fast in progression, you come up on a boss that no one's done a write up for yet, and that means you've just become a guinea pig. This learning process is necessary, so try and grin and bear it with good humor. Also try and keep in mind that fights you have done, and learned, can still wipe you. Prince comes to mind again: you can have 18k health on your MT, well geared DPS, the healers are prepped and easily breaking 1700 +heal, everyone knows their positioning and yet you still die. A heal is a fraction of a second late, a bad enfeeble/infernal combination kills the melee DPS and suddenly you're barely even scratching the Prince, Shadow Nova comes at a really bad time. These things happen.
It's really important that a tank doesn't let his or her frustration show as anger. It's okay and understandable to be frustrated when you wipe five times on a boss you've killed before, but yelling at your raid isn't going to get the thing dead. Trust me, if yelling killed bosses, the mute function on my headset would be like unto a god and I'd be dripping in legendaries.
Not much else to say, I guess. You have to meet the gear requirements, then constantly upgrade as new gear requirements come in for new encounters, always upgrading your health pool, your mitigation stats and your aggro generation stats. You have to make sure you're prepped with food and consumables. You have to research the fights, learning about abilities like Charred Earth or Empowerment. And you have to keep your cool throughout the whole process, despite the understandable urge to rip the headset off and scream profanities at that one guy who won't stop moving during Flame Wreath. And the reward is, once you kill the guy you're on now, you get to do it all over again for some new dude whose crotch will be in your face for most of the fight!
Don't all run off to start grinding your tanking gear at once, I know I make it sound so glamourous.
Next week we switch gears and talk about DPSing.