IMO, people would be much better players if they would level (at least in dungeons) as the role they intend to play at max level. Too many people who plan to tank or heal level as DPS because it's "easier," only to have no clue what they're doing when they get to the level cap and try to hop straight into content designed for that level.

Nothing gives you insight into the tools of your class for the role you want to play like learning them gradually along the way. Having them all dumped into your lap at once can be very overwhelming.

I agree to a point, but saying "the best way to learn to tank is to level as a tank" doesn't help max-level people who are interested in tanking.

If you are max level and want to learn tanking, queue for Throne of the Tides and Blackrock Caverns normal runs. You will outgear the content and the rest of the group by a wide margin, so threat and survivability won't be problems. All you have to focus on is using your tools.

Then work your way up through the harder ones until you reckon you can handle heroics.

Along the way, pretend you are running the heroic version, and that any stray mob would kill whoever it's on. This will give you a sense of how well you could handle the situation if it was a heroic.

Practice target marking. It's silly for an 85 warrior tank to be marking targets in a lvl 80 normal, but at the very least get used to making a kill order. DPS are practically incapable of targeting your target, and choose their next target at random (not limiting it to the current group). They understand skull and X, however, so if you put those out there they might behave.

It doesn't matter in your practice norms, but it will as you start heroics, so it's a good habit to have.

If you have a really gung-ho DPS who opens with his highest damage/threat ability always, assign him a CC target and ask him to CC after you pull. This gives you at least one more GCD to establish threat and get the group under control. Think of it as CCing the DPS, not the mob.

Same goes for people who can't stop their AoE threat. If you have a party of 5 and a cleave that hits up to 3 things, CC two of them so that the AoE doesn't overtake your threat. CC is not always about limiting the damage you take as much as it is about keeping a leash on your DPS.

That doesn't really help those of us who levelled a hybrid a long time ago and never thought we'd be tanking with it. My paladin was always ret/holy, but after dabbling in warriors and druids at low levels I read something that said paladins were EZ mode tanks (in wrath anyway). I thought that might be an easier place to start, especially since all the dungeon finder groups I encountered at low levels didn't really let me tank. They were super impatient and wanted me to pull multiple groups without giving me any engouragement or information on how many groups I could handle. I certainly didn't know, and wasn't too keen to push my limits with a group that would likely get mad if I didn't know that 2 packs is the right amount and 3 is a wipe, or whatever. So I'd get healers leaving, dpsing, pulling packs for me, all the dps pulling for me while I was looting...

The low level dungeon finder isn't a fantastic place to learn to tank I don't think.

@Katherine

Welcome to tanking. DPS are often rude and obnoxious with a healthy sense of entitlement. They are also annoyed because it took them a 45 minutes to get the run, and they are going to take it out on you.

The real impediment to people learning to tank are the very people screaming for more tanks.

I would like to say it gets better, but I have those same idiots in heroics, along with several other kinds up to and including the full-heroic-geared DPS who want to show that they apparently managed to go through all that raiding without any understanding whatsoever of vengeance mechanics.

Tanking requires a thick skin as well as armour.