Warrior Rage Mechanics
The basic defining characteristic of the Warrior class is the Rage mechanic. You will use (or gain) Rage for nearly all of your abilities. You'll need Rage to attack your opponents and to defend yourself, to apply debuffs and to buff your party. (See III - Abilities for a more detailed description of your abilities and their rage costs).
So... how do you gain Rage? Rather simply, actually - barring a few special abilities and potions (namely Charge, Bloodrage and Rage Potions) the only time you will gain Rage is by either dealing or receiving damage. I've included a more detailed description of the exact Rage mechanics at the bottom of this section in the Math Sidebar, but for the moment that basic description will suffice. You'll gain rage by either beating the crap out of your opponent, getting the crap beaten out of you or some combination of the two.
Of course, this has several interesting implications... namely that the more damage you deal or receive, the more damage you'll deal due to the greater Rage supply. This is one of the aspects that makes Warriors so deadly in PvP - should you get a beating but survive it due to a support class healing you, you'll come out of it with a full Rage bar and the ability to beat the smack out of the next thing that comes close to you. This is also the foundation of the "warriors scale better with gear" line that you've probably heard bandied around a lot - and it does apply, as more damage creates even more damage from the additional Rage generation.
Math Sidebar!
Prior to the 2.01 patch, Warriors gained rage according to some rather simple formulas. Namely;
Rage Gained = Damage Dealt / (Level * .5) - or Rage = Damage Dealt / 30 at level 60.
Rage Gained = Damage Received / (Level * 1.5) - or Rage = Damage Recieved / 90 at level 60.
I should state that, for the sake of completeness, these formulas are likely to only be approximations. According to some of the Blue posts, the actual coefficient at 60 should be Damage Dealt / 30.75 - but it's 'good enough for government work', as the saying goes, to use the old formulas as they were understood.
After the 2.01 patch, the formula for Rage generation was changed to a new formula that 'averages out' the rage generation with a fixed number based upon weapon speed. Interestingly enough, the Blue post used the following formula;
For Dealing Damage:
Main Hand Normal Hits: Factor=2.5
Main Hand Crits: Factor=5.0
Off Hand Normal Hits: Factor=1.25
Off Hand Crits: Factor=2.5
Rage Conversion Value (note: this number is derived from other values within the game such as a mob's hit points and a warrior's expected damage value against that mob):
Rage Conversion at level 60: 230.6
Rage Conversion at level 70: 274.7
Expansion Rage Gained from dealing damage = ((Damage Dealt) / (Rage Conversion at Your Level) * 7.5 + (Weapon Speed * Factor))/2
...and that formula is complete and utter crap. It was, as far as I can tell, written in such a way as to use as many idiot coefficients and to make it as confusing as possible to the average viewer as to be worthless. Note the apparently random use of the 7.5 multiplier... and... well, it's idiocy. A much, MUCH cleaner way to write the new formula is;
Rage Gained = Damage Dealt / (Level Coefficient) + Weapon Speed * 1.25 - or Rage = Damage Dealt / 61.5 + Weapon Speed * 1.25 at 60
Which has all sorts of interesting side-effects. The most important side-effect was the massive, unilateral nerf to Warrior rage generation. Notice how low the weapon speed multiplier is? With a 3.8 speed weapon (such as The Unstoppable Force), you will generate 4.75 rage per swing that deals any damage, with the remainder of the rage coming from the damage dealt. Of course, in order for the new rage generation system to be equivalent to the old one, you'd have to have generated 9.5 Rage on a normal hit with your Unstoppable Force... which works out to an average hit of 285. Or, to put it another way, you'd have to be using the Unstoppable Force while naked, without Battle Shout and with your innate character Strength gained while leveling somehow removed via a debuff. Even if you factor in Endless Rage (which requires a 41-point Arms talent), you'd have to have had an average hit of 356 - so you can use Battle Shout, but still no armor.
If someone tells you that their rage generation went up as a result of the patch, they are full of shít. /rant off
Math Sidebar Addendum!
As of 2.0.10, Blizzard got their head out of their collective ass and rebalanced Warrior Rage Generation to a reasonable number once again. The weapon speed numbers were adjusted upwards to 3.5 on a mainhand hit, with the same ratios applying (7.0 on a mainhand crit, 1.75 on an offhand hit, 3.5 on an offhand crit). This makes the new formula;
Rage = Damage Dealt / 73.2 + Weapon Speed * 1.75 at 70
