BM Damage

From the pet right?
Not completely, while a BM's pet is the strongest of the three specs, that is not the only way that a BM hunter is able to do large amounts of damage.
Let me start off by saying that I have nothing against the Marksman or Survival Specs, and this is not in any way an attempt to say that BM is better. I play BM because that is what I like, not because I'm convinced that it is the "best" spec.
So lets look at the talents that a BM hunter has that make the damage fly.

Improved aspect of the Hawk: 5/5 While Aspect of the Hawk is active, all normal ranged attacks have a 10% chance of increasing ranged attack speed by 15% for 12 seconds.
From personal experience (and I could be wrong) I've found that during long fights (anything over 30 seconds) where I'm not running around trapping but able to stand a DPS, the haste buff from this is on about half the time, which amounts to an approximate 7.5% DPS increase from these 5 points.

Focused Fire: 2/2 All damage caused by you is increased by 2% while you pet is active and the critical strike chance of your Kill Command Ability is increased by 20%
OK, we're going to ignore the Killl Command part of this talent right now since it's a pet attack. The first part however, means a 2% damage increase on ALL damage, just for having my pet out. It could ba a level 1, just tamed, untrained pet, and I'd still get the damage buff.

Ferocious Inspiration: 3/3 When your pet scores a critical hit, all party members have all damage increased by 3% for 10 sec.
While this one is dependent on the pet getting a critical hit, as long as the pet is level 70, trained decently and fighting, it will have a crit withing the first 10 seconds, and from then on be able to maintain the buff as long as it's alive. And that 3% counts for ALL damage for ALL party members. Now this one I will say is the best party buff of the three trees. Why? It is the only one that helps casters as well as melee, Trueshot Aura add 125 Ranged and Melee Attack power and Expose Weakness adds 25% of the hunters Agility as AP to all attackers on the mob the hunter just critted. Neither of those give anything to spell damage and neither scale as well as Ferocious Inspiration. While the 125 AP or 25% of hunter's agility to AP would mean quite a bit to a warrior in all greens, a warrior in mostly all/all purples would not gain as much. But FI would give both of them a 3% damage boost.

Serpents Swiftness: 5/5 Increases ranged combat attack speed by 20% and your pet's melee attack speed by 20%.
This is the #1 damage buff that a BM hunter gets, 20% attack speed increase=20% base DPS increase.

The Beast Within: 1/1 When your pet is under the effects of Bestial Wrath, you also go into a rage causing 10% additional damage and reducing mana costs of all spells by 20% for 18 sec. While enraged, you do not feel pity or remorse or fear and you cannot be stopped unless killed.
A 10% damage increase for 18 seconds every 2 minutes. Doing the math means that over a 2 minute fight, the hunter gets, overall, a 1.5% increase in DPS.


Shot Rotation
With the increased speed that a BM hunter shoots at, they do not have the time to put more than one shot in between each of their autoshots without delaying the autoshot. Because of that, the typical shot rotation for a BM is Auto->Steady->Auto->Steady... I normally use this because Steady has the best damage-to-mana ratio. Using only Steady Shot lets me use Aspect of the Hawk for more DPS and still be able to maintain mana with pots and drinking between fights.


BowX-bow/Gun speed
To a BM hunter, the bow speed is very important to their DPS, with the haste buffs from Serpent's Swiftness and a 15% quiver, a BM hunter's weapon speed is reduced by 27.5% without IAotH up. That turns a 2.7 weapon speed into a 1.96 or a 2.8 weapon speed into a 2.03. This allows the hunter to shoot a Steady Shot between each autoshot without delaying autoshot, with just enough time for latentcy and IAotH. Steady Shot is a special shot that causes [RAP*0.2 + 150 + Average Weapon Damage] damage. To get a weapons

Average Weapon Damage (AWD) just multiply its DPS*Speed.
Now for chart time:
For this I'm going to use 65 DPS as the base DPS for the weapons, 2.7 and 3.0 for the weapon speed and 1500 for the RAP.

Speed---Mod Spd---# of Steady/min---Steady Dam/shot---Steady Dam/minute
--2.7-------1.96--------------30.6----------------625.5---------------19172-------
--3.0-------2.18--------------27.6----------------645-----------------17793-------

The extra Steady Shots with the quicker weapon ended up with 1379 more damage in one minute, that results in an almost 23 DPS increase. This is of course ignoring misses and critical hits.