Check this out, via World of Logs, which allows you to compare with the top players in your class and spec on a by-encounter basis (Destrolock shown here for example, click your specific spec):

http://www.worldoflogs.com/rankings/players/Baradin_Hold/Argaloth/10N/Destruction_Warlock/

Warlockery: A Primer on Playing a Purple Square (current 4.0.3)

The goal here is to compile several key sources of information about how to most successfully play a warlock in PVE. I'll try to remember to head back here and update things as Cataclysm progresses. First a few caveats: 1) I use ElitistJerks, MMOChamp, WorldofRaids, and so forth, as sources; if you're looking for an original source start looking in those places. 2) If you have a comment, you're welcome to make it. If you're just looking to prattle on about what you "feel" should be a better (fill in the blank: gem to use, spell rotation, stat priority, etc) I'd very much prefer you keep your unresearched opinion to yourself. IF, however, you've got some solid math and/or reasoning to show that I'm wrong PLEASE DO comment and let me know. 3) Each and every one of my comments is aimed at increasing Raid DPS. I understand that personal DPS is one of the most important components of Raid DPS; however, Raid DPS is ALWAYS the end goal of the warlock.

I've been asked to play Destruction in my 10-man (primarily to have a source of replenishment as well as some other buffs), however, I'll do my best to focus this guide on more general warlock guidance as there are some new things to consider in cata. 

Dark Intent

By now, you've become familiar with Dark Intent--the new warlock buff. For the uninitiated, here's what it does:

1. It applies a 3% haste buff to both the casting warlock and that warlock's target (cannot be self-cast). This does stack--that is, if there are 2 warlocks in raid, and they "trade" dark intents (like mages traded focus magic) they will indeed stack additively to a 6% haste buff. Don't do this. It's stupid. Very stupid. Why? See point 2.

2. Dark Intent also applies stacks of dark intent. Stacks are applied on your target when one of your periodic damage attacks is a critical strike. When the target of your dark intent crits with a periodic DoT (or HoT), they apply one stack of dark intent on you. Each stack of dark intent equates to 3% additional DoT damage or HoT healing up to a maximum of 3 stacks. The reason "trading" dark intent is a bad idea is that regardless of how many times you have the dark intent buff on you, one character can only gain a maximum of 9% increased DoT damage or HoT healing. By trading the buff (with one other warlock), you're essentially giving only 2 people 9% increased periodic damage or healing, while you could have 4 people with 9% increased periodic damage or healing.

Who do I cast dark intent on?

This post answers that question in some detail. In short, given that healers are doing much to conserve mana, they may not be throwing out HoTs like they did in Wrath. Their good play may actually make them a less desirable target for your DI. If you cast DI on a healer, it should probably be a resto druid or a raid healing holy priest.

One of the fun things about DI is that it allows for certain class synergies in raids. For instance an affliction warlock who DIs a shadow priest adds about 4.1k raid dps (in iLvL 372 gear). Meanwhile, the identical affliction warlock who DIs a boomkin gets about 3.4k extra raid dps. Here's the cool thing about that: If said affliction lock looked only at his or her own personal dps gain, he's likely to choose the boomkin--he gains more from buffing the boomkin, but the raid loses 500 dps.

Moral of the story: Do - read the above linked post and maximize your Dark Intent usage based on your specific raid's requirements. Don't - be a selfish fucktard who ends up costing your raid 500 dps because you want to squeeze out an extra 9 dps.

Fel Flame

We got green fire!!!! Ok, are you over it? You should be. How cruel is Blizzard to give us green fire in a spell we NEVER cast. MAYBE cast this when you're on the run. OR, if you've got some hella awesome haste buff from something that you want to keep on immolate or unstable affliction. Mostly, this doesn't get cast.

Raid Buffs

Food: You'll most likely be using Severed Sagefish Head (Deepsea Sagefish can be caught, relatively reliably, off the shore of Twilight Highlands--don't look for schools, just fly out to a wrecked boat or small island and cast off) although if you're short on hit you may also opt for Grilled Dragon, and finally, IF you're desperately trying to get to the 50% haste threshold to get another dot-tick you might opt for Basilisk Liverdog. Note, intellect is the best stat a warlock can get, I believe this is true regardless of what spec you play. As a general rule of thumb, your dps will go up more per point of intellect than anything else. It's going to be the safest choice to use +intellect food.

Flask: Flask of the Draconic Mind. Hopefully you knew that already.

Pot: Volcanic Potion. Again, a no-brainer.

Hit Rating

Things changed for Warlocks (and many other DPS casters) with Cataclysm. Hit no longer provides the most dps per point up to the hit cap. (This may be true-er for Destro than other specs, I can't say for sure...ok, I just went and double checked and now I can say for sure). For both pre-raid 346 and late T11 372, Intellect is more important than Hit. What this means is that there may be some circumstances when it's okay--and where you'll bring more damage to the raid--by NOT being hit capped. It's not like hit is something you'd need to avoid, it's just not something one needs to obsess about. This is a substantial change, as I understand it, from the way warlocks have been in any previous release (I didn't play in vanilla, but from what I read, this was not the case).

Presently, the spell hit cap is 1742. Because all gear a warlock would use has Int on it anyway, I've been gemming to hit the hit cap as well. However, I've been careful to use +int +hit gems rather than straight hit gems, in most cases.

Enchants

A post over at EJ (which can be found here) details what you should use, materials and money permitting. One note of disagreement I have is with the glove enchant he suggests. While I do believe that Jmickey (the author of the thread at EJ) is right about the optimal Cataclysm enchant, I think that according to scale values the old Wrath +28 spell power should provide the greatest dps increase unless one was using that particular haste enchant to bump them over a threshold.

Based on the latest simulationcraft outputs as of now, the most conservative haste : spell power scale value ratio is the 372 BiS geared affliction warlock. That ratio is 1.4442 : 2.5882. Meaning this: the glove enchant should, unless I'm missing something here, return 72.21 dps for the haste enchant and 72.46 dps for the spell power enchant. For all other gear levels and specs the difference is more pronounced in favor of the spell power enchant.

Haste Thresholding

I'll probably have to add more about this later too, but I've alluded to the idea of haste thresholds above. They're pretty important, so I'll mention them in some more depth here. Primarily, haste thresholds have the greatest effect on Destruction Warlocks because of the way that haste affects immolate and the way immolate affects the destro nuke, Conflagrate.

I'll make it easy. When you get enough haste, you get an extra tick of immolate. Without any haste on your gear, just through regular raid haste buffs, you'll probably get an extra tick of immolate. You'll only need 10% haste to achieve this. The next threshold is at 581 haste (30%). At 2639, you'll hit 50% haste and get 3 extra ticks of immolate. For present gear levels, a destro lock will probably end up being best off at 581 haste...that extra 2000 haste is just going to be a rough grind with current gear.

Crowd Control

Although you haven't used it for an expansion, it turns out, you do have some crowd control. You can fear humanoids and banish elementals and demons. Please don't fear things without glyphing into fear. You may only fear one target at a time. Same with banish.

With new warlock Banes and Curses being separate, it occurs to me that most fights will have an optimal warlock curse debuff depending on boss abilities.

I'm presuming that we'll never be using CoE as it should be brought by someone else in raid. Meaning the choice of curses is between Weakness (10% physical damage mitigation) and Tongues (30% casting time increase). This will serve as a placeholder and I'll throw out some conjecture based on Saedo's strat pages:

Magmaw: Curse of Tongues

Omnitron Defense System: Curse of Weakness

Chimaeron: Curse of Weakness

Atramedes: Curse of Weakness

Maloriak: Curse of Tongues

To be continued...

I'm bored at work so I'm going to use this as a place to compile some raiding Warlock thoughts for until Cataclysm. I'm not going to do a Demo spec at the moment because, well, I don't really see it as raid viable yet so long as an elemental shaman is around the sp buff is now the same.

Word of Warning: This guide is in a state of constant flux as what's live is also in a state of constant flux. For example, presently Demonology is testing as the second strongest DPS spec, ahead of both DL and SB affliction locks...so I may need to write up one of those guides soon. We'll see.

Destruction

Destro looks to be the top warlock spec at the moment, even after the nerf to Searing Pain (which you had to know was coming).

Glyphs: Top main performing prime glyphs are Conflagrate, Imp, and Immolate

Other valuable major glyph: Lifetap (unless your haste is high...1400ish).

Fear, for CC issues is nice too. When glyphed targets cower in terror rather than run around and pull mobs.

Gear: First, get up to 17% hit. 446ish. Remember spirit is worthless, dump your purple purified dreadstones for veiled dreadstones (int / hit). Reforging is okay if you have gear with crit on it, but in many cases it won't be that helpful, since you've probably been stacking haste for the last little while anyway, haven't you. If you can reforge hit (if over cap) or crit to haste or mastery, you should do so. Haste is very slightly better than mastery at the moment, unless you're over the 1406 haste cap. Anything beyond that point should ABSOLUTELY get reforged into Mastery. But, let's be honest...you're only at that point of haste on your gear w/o any more spellstones if you're mostly 277/284 gear...and those folks aren't probably the kind of person who needs to read guides like this.  :)

Spec: Pick the dps talents as much as possible to 31 in Destro. Then hop over and pick up some points in Dark Arts and Imp Corruption.

Pet: Imp

Rotation:

Start with a Shadow Burn --> Soul Fire to keep up the Imp SF buff (15% haste buff for 15 seconds if target is over 80% health).

Keep these dots up all the time: Immolate, Bane of Doom, Corruption.

Keep Conflagrate and Chaos Bolt on CD.

Use your instant cast SF when it procs.

Pop Doomguard / Infernal (for multi-targets) if it's up.

Collect loot.

EDIT 3: Neither edit 1 or 2 was helpful. Things are correct as originally posted.

Affliction

Affliction is still a strong contender for a dps spec. Many things remain the same in terms of rotation for affliction. There's technically a viable Drain Life spec which is very different than the Shadowbolt spec. The thing is, if you want to be a DL warlock, your reforging is very different than either a SB afflock or a Destrolock. That means that if you want to be at an optimal level you'd have to reforge if switching between DL Affliction and Destro or SB Affliction.

Personally, my dps has been about equal between DL Affliction and SB affliction and I like to be able to switch to destro, so SB is the way I'm choosing. DL is substantially harder to play and requires you to micromanage each and every facet of your gameplay (no simple button spamming for your filler spell, your range from the target is a substantial issue in order to keep up your 15% dot damage debuff, lots of math in terms of figuring out when to "clip" DL). All in all, if you can manage all that, knock yourself out...but Ghostcrawler says you'll be casting SB again in a few months anyway.

Glyphs: Haunt, Bane of Agony, Lash of Pain

Other major glyphs of importance: Shadowbolt, LifeTap (until haste > 1400). Fear, for CC issues is nice too. When glyphed targets cower in terror rather than run around and pull mobs.

Spec: Pick all the regular dps shit in Affliction to get to 31. You'll have to pick some optional stuff. I only put 1/2 in Jinx as Jinx has only really valuable application on trash. Same reason I skipped on the Seed of Corruption talent. I did pick up Curse of Exhaustion, for potential kiting. Then I grabbed 3/3 Bane and 2/3 Shadow and Flame in the destro tree.

Gear: Here's where DL and SB playstyles vary. The reason DL is viable is that it benefits from mastery. If you switch just about every piece of gear (after hit capping at 17%) so it has mastery on it, you get an added 33% (ish, that's what it was for me) periodic damage increase. What that means is that essentially ALL your spells have an extra 33% damage bonus.

For either DL or SB you should be dumping spirit. (As above). Gearing for a SB focus the stat weights are basically the same as for Destro gearing as described above. (Mastery is a little more valuable for Destro locks than SB afflocks, but probably not so much that it changes gear sets between the two.)

Pet: Succubus

Rotation:

Starting off, it's no longer as valuable to stack Shadow Embrace with shadowbolt and haunt, so you're just as well starting off by throwing up your dots on the target as you run in because dots automatically readjust to crit, haste, and spellpower levels upon refresh.

Keep Haunt on CD at all times.

Get up your Dots (Bane of Agony, Corruption, Unstable Affliction).

SB filler (or DL if you're a drain life focus...also as DL you probably will need to stand way closer to the boss so you don't lose Shadow Embrace w/ Haunt's long travel time...you'll also need to keep an eye on the 5% crit debuff if you're the only one bringing it--see, I told you it was hard).

When boss is <25% health, use Drain Soul (which can now crit) instead of ShadowBolt.

Pop Doomguard when available.

Pretty much the same rotation as before for SB focus.

After Saedo posted the leaked talent calculator from MMO Champion that outlines the talent "changes" for Cataclysm. I started rooting around a bit just to see what things might look like.

Of course, almost all of this could change, I haven't gotten a good feel for what the mastery system might add or tweak talents, but here are some very preliminary thoughts.

1. Not much change in any of the three trees.

2. Unless they really make Elemental shaman's Totem of Wrath competitive, there's not much change likely in terms of having a DP warlock in most raids. We're just going to be a fixture until ToW competes. ToW will certainly see some buffing in Cata, the question is if it will be so substantial of a buff as to make the DP warlock ineffective. I'm guessing not, or at least not for long. With that said, I'm envisioning this sort of talent tree as a demo-lock. Getting down to devastation could be a nice boost, how valuable this is, though, depends on how well crit scales and how this works with the mastery system.

3. I hate to say it, but a secondary spec that seems, at least initially to be a winner in the new xpac could well be a shift back to destro. The main change I see here would be Destro locks would finally have the ability to get down to master conjurer. I envision something like this. Also, the destro tree might find itself with a bit more flexibility to pick up talents which could potentially buff various pet utilities. If they're hoping to make pets more interesting in Cata, the most flexible spec here to use a variety of talented pets might well be destro.

4. Affliction looks to be about the same as it's always been. I see the big change there as a spec down to devastation (same as demo). Bottom line though, in order to get down to devastation, the afflock ends up taking a lot more unuseful talents along the way. Something's probably going to change here...I think that an affliction spec basically requires 5 points to get devastation, might not be the best option.

So, I'm sure lots will change. I hope so. These changes seem really run-of-the-mill for us at the moment.