DeathKitty Tanking Guide Part 1: "So you want to be a Bero..."
I hope at least one person gets that reference.
In order for me to impart my knowledge and experience unto others, it's important to start from the basics - From the most basic functions and actions which make a tank what he/she is. With that in mind, what exactly is a "tank"? What do they do? What do they not do? How do they know when to do what?
Those are the sorts of questions that a lot of people and/or tanks out there don't really understand or know the answers to. If you don't know these simple things you can perform the task of being a tank, but you'll never have the awareness to be exceptional at your role. However if you do, there's nothing you won't be able to beat.
What is a "tank"?
A tank is someone beefy. That likes getting beat up. Like an actual tank.
In all seriousness though. A tank has 3 main responsibilities:
1) Make sure the right big baddies are hitting him/her and not the squishies.
2) Make sure said baddies keep hitting him/her until they die or circumstances change.
3) Do their best to not die.
#3 tends to disqualify pretty much everybody that isn't built to tank in the first place. It's fairly easy to make people hit you as any class, and still fairly easy to make them keep hitting you. It's hard to stay alive while doing so. Thus you end up with specific talent trees in specific classes that with the correct items, are designed to survive a long time in that situation.
What does a "tank" do?
To examine this, lets simply elaborate on the previous three responsibilities.
Make sure the right big baddies hit you.
If you've been playing any sort of MMO for any length of time, you'll know that certain fights can have many different monsters in them. As a tank, it's important to know which ones you are supposed to have beating on you, and which ones you're not. A simple example to illustrate this would be the Blood Prince Council encounter in Icecrown Citadel. The tank that is responsible for tanking Valanar and/or Taldaram never wants to have Keleseth turn around and start casting Shadowbolts at him. This will usually constitute an instant death.
Make sure the baddies keep hitting you.
It's one thing to get something to start hitting you, it's another to make it keep hitting you. You need to know the best way to use your abilities to maximize the amount of burning hatred the baddie has for you. This is a term called "threat". The more of it you have, the more damage or healing someone has to do to make the guy angry at them. Remember the goal is to have the baddies hit you, and not the squishy ones in the dresses.
Most big bad boss monsters have an ultimate abilitiy that they use to inflict severe pain on whoever they are hitting. In some cases the healers will not be able to keep up with the level of incoming damage. In these cases a tank would burn a "cooldown". That is they would use an ability that reduces the amount of damage they receive for a short period of time. Doing so allows the healer(s) to catch up with the incoming damage and prevent you from dying. This is a good thing, because if a tank dies everyone else usually quickly follows suit.
Which brings us to....
How do you know when to do what?
Honestly, this is more practice more than anything. I've tanked for about 3.5 years across 3 different sets of raid content. I've done 40 person raids, 25 person raids, 20 person raids and 10 person raids. They're all different and they all require you to adapt. Even 5 person dungeons are different from each other. The way you learn how to properly tank an encounter is simply through repetition. However there are certain skillsets and knowledge you can learn without repeating an encounter over and over again until its drilled into your skull.
That will bring us to Part 2...