Things Warriors Want Non-Warriors to Know
* Don't run away from us if you have aggro.
* Let the warrior do the initial pulling unless you are using a hunter to create the Perfect Zone of Ultimate Safety. It's easier to hold the aggro when you start with it, than trying to pull it off someone. Sure mages have some amazing ranged spells, as do many others, while the warrior's ranged ability is mediocre at best. If a mage opens up on a mob by doing a couple thousand damage, its hard for a warrior to overcome the hatred that creates in the mob. In the event it appears that the best tactic would be to have someone else pull, use a low damage low hate spell. Whatever you have that does the least damage is good.
* Wait to start fighting mobs until the warrior has their attention with a shout and swing or two. Stunning or immobilizing an enemy while we're trying to drag them all into a nice spot can easily lead to us missing them, and starting to unload damage before we've hit them often means they'll start running at you.
* If we're not in melee range, we're not doing damage, we're not generating rage, and most important of all, we're not getting aggro. Please do whatever it takes to force the mobs into close combat. Never think it's acceptable to trade fire from across the room. Mages can use Counterspell to stop a mob from casting. Normally they only have one school, so after the interupt they will run into melee range. Be carefull tho as Counterspell generates a good amount of threat.
* If we are holding aggro, healers, your first priority is to keep us healthy. When the tank dies, the party dies. Tell us if you are getting Out of Mana and the end of the fight is not yet in sight. Then we can use abilities like shield wall to stay alive. Often we are so busy with tanking we forget to mind our health.
* We can tank without a shield. It does require us to have better gear than the average warrior at that level or to only do it on the easier section of the instance, but it can make things quicker and lets us hold aggro better (assuming we're still in Defensive Stance). If you're getting bored healing, let your tank know--it can make clearing out the trash mobs a faster and more painless process.
Some class specific notes
Paladins - Make good use of your auras. If we're dying, Resistance or Devotion Auras are nice, but if we're losing aggro, Retribution Aura might be nicer. Also, we know Blessing of Kings is in your Protection tree, but it's simply amazing if you have it.
Hunters - We know you're good at pulling, but it's a lot simpler to let us do it in most situations. Offer to pull in dangerous situations where there's a big chance for problems (lots of or fast moving patrols, many close enemies) but please don't be too offended if we'd rather do it ourself. If you really want to pull and you have the misdirection spell offer a misdirection pull as that will dump all aggro on us.
Druids - Thorns is nice, please don't forget to cast it on us. Also, even if you aren't the healer, if you aren't the tank please resist the temptation to turn into a bear and use Growl/Maul on everything. It makes it much more difficult to hold onto the mobs, since you have naturally increased threat in that form.
Rogues - If you use Expose Armor, we can't use Sunder Armor on that target. If we can't use Sunder Armor, we have a hard time holding aggro. If we have a hard time holding aggro, the mob has a tendency to turn around and squish you. Also, be aware that stunning a mob means it isn't hitting us, and not giving us any rage. While it won't be a danger to anyone, there's a good chance that it'll turn to you when the stun wears off. And please resist to stun mobs during the pull it makes tanking a lot harder for us.
Mages - Please don't blink away when you pull aggro. We can't move that fast, and it tends to make it difficult to get a hold of all the mobs again. If possible, don't rely on a macro that says your target's name when you polymorph. We don't usually have time to read names in 1.5 seconds, and sometimes there's more than one of them anyway. Instead, teach your tank what Detect Magic looks like and cast it on a mob before sheeping it. Visual clues are a much bigger help. Raid Icons are usefull to i.e. Moon gets polymorphed.
Warlocks - When in doubt, please bring your Imp. Blood Pact is a really awesome buff, giving healers more time between us being at full health and us being dead. At the same time though, don't be afraid to pull out a Voidwalker, Succubus, or Felhunter if you think their skills will be useful in dealing with the mobs. Also, we'd like a healthstone if you've got shards to spare.
Priests - Don't use Power Word: Shield on us more than necessary. Yes, it's a useful tool to save us from death, and it's convienient to just keep shields up while dealing with easier enemies. However, it severely cuts down your typical tank's rage generation, making it very frustrating to try to hold aggro. However please do use Power Word: Shield before a boss fight as the boss will hit hard enough to knock down the shield fast but you don't have to heal us for the first few seconds giving us the chance to build some solid aggro so you won't pull the mob off us with a critical heal.
Things Non-Warriors want Warriors to know
* The first thing that every warrior in an instance group needs to accept is this: you are not there to do damage. Any smart group would rather you do zero damage but keep aggro on you at all times than to try to keep your dps up and let the mage or healer get beat on. It is possible (even easy) to hold the attention of 2-4 mobs at once, but not while you are trying to do damage to the enemy.
* Always have Sunder Armor on your action bar. Regardless of your preferences, you have considerably more armor than most casters have, and Healers will have a much easier time healing if only you are taking damage.
* If you're tanking, be in Defensive Stance for most of the battle, unless you are using Tactical Mastery to switch stances to use special abilities. Also, if you have Tactical Mastery, in some pulls, charging the mob then switching right to Defensive Stance can be a very effective way to generate your initial rage, which is the hardest part of the battle.
* There are several skills that a warrior needs to have in an instance group to survive. The first of these is aggro generation. There are three skills that do this best, Shield Bash, Revenge (much more efficent with talents), and Sunder Armor. These three skills are what you use to keep aggro on yourself. When this fails, Taunt is your best friend, and will buy you a few seconds to regain aggro (with Shield Bash or Sunder Armor).
* Another skill that is rather simple yet many warriors do not use, is "tap" aggroing. When there is a pull of multiple mobs, they will have no one on their aggro list, and run to attack the nearest party member. An easy way to stop this is to use Demoralizing Shout to gain a very small ammount of aggro on all the mobs around you instantly. While the mobs will still run for your healer when they start healing you, it gives you time to use skills like Whirlwind, Sunder Armor, Shield Bash, and Revenge to gain a stronger hold on aggro. A good warrior can pull 4 mobs and never let one leave him. A poor warrior focuses on 1 and lets his group deal with the rest.
* Remember that it is your job to protect the rest of your group. However, when bad things happen (and they always do), it is important to know which party members need saving first:
1. Main Healer - Always, without fail, protect your healer above all else.
2. Cloth Wearers - They die fast and need attention before their mana is depleted.
3. Druids/Shamans/Rogues/Hunters - Have Leather Armor or better, and either heals or ways to lessen their own aggro. Can all off-tank in bad situations when the healer needs saving, but don't count on them to do your job for you. If the Druid or Shaman is main healer, get the mob off them first.
4. Paladins - Unless they're your main healer, Paladins are tanks themselves, and can off-tank an elite mob if needed. If they are main healer, help them first.
* While it can be argued that you are perfectly capable of pulling, you are not going to be the best puller in every situation. A great resource on knowing when you are the puller is The Perfect Zone of Ultimate Safety. Basically, a Hunter or even a Rogue can attempt a pull while the rest of the party is standing out of aggro range, then if it works they will be able to hand aggro to the Warrior. If the pull goes bad, they can abort it or just die and be ressurrected later. This can be a slow tactic and may even be impossible to pull off at the time (cramped space for example).
* If you are the primary tank, use a shield. With a shield, in some cases you can get close to 3000 extra armor, a few more stats, a shield spike or enchantment, and + defense to add on to what you already have.
* If you are tanking a mob near a shackle, sap, polymorph or otherwise incapacitated mob please consider pulling the active mobs away before using any AoE abilities like Thunder Clap. Also consider moving away so that other members of the group with AoE will not hit the crowd controlled mobs.
* Do not become overly aggresive. Don't go rushing into battle whenever you see a mob. Let casters recover mana and allow for rebuffs. You can't last long if healers and damage dealers are tapped out and can't recover while in combat.
* Healthstones and Healing Potions are in the game to be used, so use them!
Things Warriors want new Warriors to know
* If there is no other warrior in our party, you need to tank. Get used to it.