Destruction

Destruction is based off of high up-front damage and utilizing your top damage abilities as often as possible. Your top damage abilities will be Incinerate (your spam button), Chaos Bolt, Conflagrate (and its DoT effect), Immolate, and Curse of Doom. The majority of your talents will be focused around increasing fire damage, critical strike, and reducing cast time. Destruction has no “Cooldowns”.

Spells/Talents

http://talent.mmo-champion.com/?warlock#fPyb2XKXk-mc1,q8wOq3,11159

This is the spec that I am currently using, which means that it is not necessarily perfect for you. For example, I currently run with ~17% hit on my gear, meaning that I am always hit capped regardless of whether there is a Balance Druid or Shadow Priest in the raid or not. Since our guild almost always has one of the two (thank you, Nari) you should aim to have at least 14% hit if you are to use the spec I provided above. If you are running any lower, you will have to switch points around in order to pick up points in Suppression for the extra hit %. I pick up Shadowfury, which is an entirely unnecessary ability in terms of DPS; however, Shadowfury's stun can come in very useful in fights like Deathbringer Saurfang. The talent Soul Link is a fantastic survivability talent with the only downside being the king of the friendly fire meters consistently, leading fellow raiders to think you hate them.

Immolate

Immolate is a fire DoT ability that does instant damage and periodic damage over time. It is imperitave to keep up Immolate 100% of the time because of the talent Fire and Brimstone, deep in the Destruction tree. You should pick up the Glyph of Conflagrate to aid in keeping this ability up all of the time. The talents that benefit Immolate are Bane, Aftermath, Ruin, Backlash, Improved Immolate, Devastation, Emberstorm, and Pyroclasm. The Glyph of Immolate also increases the periodic damage of this spell by 10%.

Conflagrate

Conflagrate is a capricious ability whose damage ranges greatly. With the change a few patches ago, its upfront damage was greatly reduced, but the overall damage remained relatively similar because of the DoT effect that it now leaves behind (as well as the ability of this DoT to crit). As stated earlier, you should pick up a Glyph of Conflagrate as to not screw up your rotation. Conflagrate can only be cast on the target when there is an Immolate or Shadowflame on the target. Because of server-lag and the limits of the modern computer, it may take a few seconds before you are able to cast Conflagrate on the target. Do not waste this time waiting for Conflagrate to pop. Use a Chaos Bolt, Incinerate, Curse of Doom, Life Tap, or Corruption (if you are moving) to fill in this unwanted downtime. The talents that benefit Conflagrate are Ruin, Backlash, Improved Immolate (as Conflagrate's damage is based off of Immolate's damage), Devastation, Emberstorm, Pyroclasm, and Fire and Brimstone.

Curses

Which curse you use is entirely situation dependent and so all Warlocks should be aware of the priority for which curse to use.
Curse of Elements (CoE): If there is no other Warlock putting this up, Unholy Death Knight, or Balance Druid, use this.
Curse of Agony (CoA): As Destruction, this curse is very weak.
Curse of Doom (CoD): Great DPS boost that you only have to cast once a minute, use this if there is a 13% Spell Damage effect already up.
Cure of Weakness (CoW): No.
Curse of Exhaustion (CoEx): Go home.

Chaos Bolt

The nuke. Or at least it should be. In Warcraft 3, this ability bypassed all resistances regardless of whether the target was a demigod (ah Cenarius) or otherwise and essentially messed people up. Now, it's a slightly more powerful Incinerate on a cooldown with a faster cast time. Whoopee. Cast this ability on every cooldown and, if you can, time it with Empowered Imp procs. The Glyph of Chaos Bolt seems pretty nifty, but I'd have to change the timing on my “rotation” pretty severely so I haven't tried it yet. The talents that benefit Chaos Bolt are Bane, Ruin, Backlash, Devastation, Emberstorm, Pyroclasm, Shadow and Flame, and Fire and Brimstone.

Incinerate

Your spam button. When Immolate and a curse are up and you've already spent your Conflagrate and Chaos Bolt cooldowns, mash your Incinerate key. This will be your highest damage ability on any fight with some time to sit down and pew pew. Glyph of Incinerate is necessary, get it. The talents that benefit Incinerate are Ruin, Backlash, Devastation, Emberstorm, Pyroclasm, Shadow and Flame, and Fire and Brimstone.

AoE

It's a tossup: if you're lazy, Rain of Fire. If you are ADD like me: spam Seed of Corruption, run in and cast Shadowflame, Shadowfury as you run away, then Rain of Fire.

Backdraft

Backdraft is a talent deep in the Destruction tree that you'd be a fool to run without. It's a free 30% haste on 3 casts every 10 seconds that only requires 3 talent points. Backdraft stacks are better used for 3 casts of Incinerate; however, don't alter your rotation drastically (or risk letting Immolate drop) to get off another Incinerate cast - Chaos Bolts and Immolates or even Searing Pain are free game, depending on the situation.

Glyphs

Major

Glyph of Incinerate: Get it.
Glyph of Conflagrate: Get it.
Glyph of Life Tap: Spell Power is always good, but as your gear improves into the >232 category you should notice that most of the spirit that was on caster gear begins to disappear. Over time, your overall Spell Power will increase, but the amount received from this glyph will become lower. Eventually this glyph becomes a waste of space and you should remove it for one of the following.
Glyph of Immolate: 10% more Immolate damage = easy DPS boost.
Glyph of Chaos Bolt: I still don't know how I feel about it, but try if you'd like.

Minor

Glyph of Kilrogg: Fun.
Glyph of Souls: Mana problems? You are aware that you're a Warlock, right?
Glyph of Drain Soul: Get it.
Glyph of Unending Breath: Only good Warlocks have this.
Glyph of Curse of Exhaustion: PvP
Glyph of Enslave Demon: There are almost never enslavable demons in raids any more.

Demons

<3 Tartog.

The Imp is your ONLY option as a Destruction Warlock. The talent Empowered Imp is an incredible boost to your DPS (especially with the 2-piece tier 9 bonus). Every time this little fella crits you also get a crit. If he dies, find a suitable time to resummon him because you will most certainly notice if he is not attacking. Speccing for Empowered Imp, Improved Imp, and Demonic Power will all increase the Imp's DPS. Side Note: the first thing you should do when you get your Imp is turn off Phase Shift. This ability is a trap. If the Imp is Phase Shifted, it will not receive raid buffs and so not only will his overall damage be lower, but his crit will be too. If your Imp's crit is lower, then yours is too!

"Rotation"

There is (almost) no such thing as a rotation any more in the World of Warcraft if you are a caster. For Destruction, the priority system is fairly simple as long as you have a grasp on what each ability does for you.
1.Is there a 13% Spell Damage effect? If no, CoE. If yes, CoD.
2.Immolate (and Corruption if you are moving).
3.Conflagrate (remember that server lag will mess you up on the first one after an Immolate).
4.Chaos Bolt
5.Incinerate Spam
6.Life Tap to keep mana up.
7.Death Coil if life is low.

There are many other things that could be mentioned, but if they are really a concern then please just ask me. That's what this page is for, anyway.

UPDATE:
The periodic damage from Immolate will be critting with the upcoming patch, aparently. Drop your Glyph of Life Tap, if you havn't already, and pick up a Glyph of Immolate. This is also conditional if you have greater than 650 Spirit (aka: you roll on healer gear).

<3 you Will and your guides :3