How? Well, there are assist macros for that, or you can focus target the tank and attack the target of your focus target. There was a keybind for assist as default, but I unbound it so long ago I've forgotten what it was. I'm sure a commenter will know. EDIT: Thanks to lordmigue21, I now know the default 'assist' (attack your target's target) button is F.
4. Run to the tank. I love that video I put at the top -- well, OK, the video's pretty rubbish, and the singing's not great, but the song sums up my point very nicely. If you have aggro, run to the tank. This is pretty much Running Dungeons 101, I know, but it still amazes me how many players get aggro from something and run away out of taunt range. Sure, I can chase after you, but if mobs are hitting me from behind, guess what? I'm taking a ton more damage. Stay in range and I can taunt off you -- or even better, run and stand on me with your new friends. Then my AoE will pick up whatever is hitting you.
Healers, that means you, too. Feel free to run away again once your screen's not all red and glowy. And referring back to point #1, once those mobs have started attacking the tank, don't unleash your fiery revenge upon them for a moment or two. The tank is probably focused on beating down whatever is on the lowest health. And if you're out and about in a dungeon, try to stay near the tank. Tanks may well run off on their own; tell them to wait if you're a healer and you need to drink, loot or whatever. Especially on Echo of Tyrande's gauntlet, stay with the tank. They want to protect you -- you just need to let them.
3. Don't do things that prevent your tank from gathering mobs. I'm not talking about crowd control, which, when planned and obvious, is a great and often very necessary thing. I'm a big fan of crowd control and people who use it. I'm not talking about stuns, they're great too. And I'm definitely not talking about interrupts. I'm talking about Thunderstorm, Typhoon, Frost Nova and the like.
Picture the scene: a pack with a couple of melee and several casters. Stonecore, for example. I've been being the best tank I can be, and I've gathered them all into a neat pile for you DPS to nuke down, when for some reason, Kaboom! Off they all go, flying into walls. Now I have to collect them all up all over again. They might get distracted by a particularly tasty-looking warlock or decide the priest looks hot today, and then we have a problem while I'm running around like decapitated poultry trying to collect them.
And Frost Nova -- if I can't get the mob close enough to me to hit it with my AoE, I'm not tanking it. All this means is that I have to repeatedly taunt it or tickle it with ranged abilities so that when the Nova breaks, it heads my way, not yours. I'm sure there are reasons -- I can even understand them sometimes -- but nine times out of 10, all they do is drive me mad. However, abilities like Ring of Frost that stop mobs getting away? Especially when there are lots of them? Awesome!
2. Say nonono to gogogo. Really. Stop it. There are countless reasons why a tank might not be moving at a million miles an hour pulling everything in the instance. Maybe it's their first time there, maybe they're waiting for the healer to get mana, maybe they're looking for their buff food or eating it. Maybe they don't know where they're going. Maybe they just spilled coffee on their feet. Maybe they're just new to tanking or not very confident.
Is shouting GOGOGO going to help in any of those situations? No. Is it going to make your tank really motivated to go as fast as they can just for that one person who was rude to them? I doubt it.
A seasoned, jaded tank like me will no doubt have an arsenal of snarky comebacks prepared, but a new, timid one won't, and you just made them feel even less confident. Nice one. If you're finding the pace too slow, then politely say, "Any chance we could go a bit faster?" There might be a good reason why not. You might be able to help. Everyone might learn something. A little kindness goes a long way. Also, the inherent assumption that every tank knows every dungeon and every fight like the back of their hand is, frankly, false. We all have to learn somewhere, and tips delivered kindly will often be welcomed.
1. Let the tank pull. This relates directly to all the points I've covered above. If the pace is too slow for you, feel free to hop back into that long old queue. The tank won't mind; they just hit the Join Queue button, and they're in. And the solution to speeding up the dungeon is definitely not running ahead, pulling things, then waiting for the tank and the healer to save your sorry behind.
There are exceptions to this. If you're a DK and there's a caster hanging out over there, not CCed, zapping the healer, grab it and drop it on the tank. They'll probably love you for it. But don't be a hero. So many times, I see one lonely plate-wearer trying to take down a mob single-handed, mano a mano. Every time I taunt it, they blow some smacktastic cooldown and it goes running back to them. Sometimes it's fine, and your healer can keep you going, but these things work better when we all just do our jobs -- and unless you're in a tank spec with tanking as your role, tanking isn't your job. Unless the tank dies, then go for your life.
Why is it important to let the tank pull? Well, mobs tend to be angriest with the thing that hits them first. The tank needs to make sure to position the mobs in such a way that he can be sure nobody else is getting nuked. And one stray peeling off after an overenthusiastic DPS is a waste of a taunt that might have had a better use saving a healer.
Don't take the tanking gear
One last note -- a plea more than advice. Don't roll need on tank gear if you are not the tank. Please. Tanking drops are few and far between. Trust me, a lot more DPS gear drops than tank gear. If you have a tank off spec, then do the decent thing and ask if the tank needs it. If they need it, just greed. If they don't need it, knock yourself out, but don't roll need on drops that are like hen's teeth for tanks. If you don't want to contribute to tank rage and have a tank off-spec, then queue as a tank. You'll make the world a safer place.