Warlock PVE!

1.1 Deep affliction ( 41+/0+/18 ) http://www.wowhead.com/?talent=IEMrbRfzqtcoZxx0tM
Affliction offers good survivability and mana management , while not being nearly as gear dependent as destro. The spec does very well when wearing a gear set in the range of T4-craftables and still performs decent until one collects a full set of T5. Powerful dots and potent drains make it very useful in entry level raiding since a player can focus more on survival and other designations while still doing good amounts of damage. Dark Pact offers mana regeneration like nothing else, Suppression diminishes the impact of low hit on gear and Malediction adds a significant buff to the raid. There are many support and utility talents in the affliction tree, so everyone can make his own version of the spec serving whatever purpose he might use it for. In basis, if one solo farms a lot he can take Fel Concentration and players that like Shadow Embrace can freely take it all without impacting vital DPS talents. Destruction tree in this build isn't nearly as flexible as Affliction as you need all the listed talents for maximizing performance. In the demo tree, you can put a point in imp HS to give your raid more healthstones, if other warlocks are specced differently, or you can take imp imp for tank support.

The rotation in Affliction commonly used is as follows: CoS/E/A-> UA-> Corruption-> Immolate-> Shadow Bolt until first dots fade and then reapply and continue nuking SB. Don't bother using Siphon Life unless damage input is large and you need healing from it. For pure dps, it's not that good and you're better off dropping it from your rotation. Also, always cast Immolate regardless of the fact you probably have more shadow than fire damage bonus on gear. It's still a very powerful spell and should always be a part of your rotation. Also, there is a misconception that Drain Life is a viable part of an Affliction rotation. It couldn't be further from truth, DL should be cast only in situations when you desperately need health and HS/pots are on a CD. If you did everything right, Shadow Bolt should be 50-60% of your total damage. It's vital to squeeze out as many casts as possible rather have a second or two without a dot tick than 1 SB less.

Important stats:
Clearly spell damage and +spell hit are your most important stats, thus you shouldn't sacrifice those two stats for anything else. Remember that if you think you have your +spell hit capped because of Suppression, the talent only affects your affliction tree and most of your damage is still Shadow Bolt, which is not an Affliction spell. Do not forget about reaching the goal of 202 +spell hit ever, it should be your priority as a raiding Warlock. After +spell hit, it is spell crit and stats, prioritize them equally, but it shouldn't be too difficult considering both come with T5 level gear in abundance.

Enchants and gem selection:
When it comes to enchants it's clear which are the best enchants available for each slot as there are not many options out there. On a weapon, Soulfrost is clearly the best. Although, the cost of it is significant. When it comes to gems, pure +dmg gems are the way to go combined with +spell hit/+dmg gems. Warlocks don't have many options for metagems and since the 2.2 patch the half cast metagem has become more powerful. The Mystical Skyfire Diamond, in combination with 1 blue gem and the rest red gems, is very good for affliction specs. If you would rather stack on +hit/+dmg gems go for the +12dmg runspeed meta, since its not worth putting in blue gems to fill requirements.

1.2 DS/Destro (0/21/40) http://www.wowhead.com/?talent=IZdxczIbzZxx0tr0tVuV

A destruction spec is a lot less flexible than an affliction one. There are few possible compromises since the spec, like its rotation, is very straightforward and non forgiving. It's not meant to be a support spec. It is very heavy on mana usage and pretty low on survival, thus the gear dependency. There is no free mana through DP or strong drains, so not being in a shadowpriest group although not impossible, makes it much harder to deliver. Also, you will be petless 99% of the time, so there is 0 support value to the group. This is why you need to make sure you will not be forced to have an imp out sometimes because that will render you useless in terms of dps on those fights.

A very common misconception when it comes to a DS destro build is when people use fire. Shadow is superior to fire in every possible aspect and there is absolutely no argument for using Incinerate over SB. That is the first and most important thing one should realize. SB not only that offers more pure dps, but it also boosts raid dps by a significant amount through the Improved SB talent. Incinerate, on that account, does nothing. It is dependent on imp scorch specced mages, which are not always present in end game raids. Plus, there is a slim chance of 5 debuffs being on every trash mob or boss add immediately, which is not the case with shadow vulnerability.

The rotation for DS/Destro spec is simply spam nuking Shadowbolts while having Immolate ticking in the background. Again, same as in affliction specs, Immolate is good enough to use regardless of the fact you probably have more shadow than fire damage.

A problem that arises in destro specs is the consumption of mana and inability to regain it or to effectively regain health. That's why CD management is important. Try not to find yourself without mana and needing to tap right before something environmental in the fight is likely to hit you. With a shadowpriest in the group, these problems diminish. In most cases, you shouldn't find yourself in such survival problems anyway.

Important stats:
Since most people that spec destro already have capped hit and decent stats, damage and spell crit is the way to go. Haste is also a very good stat after 2.2, obtaining good haste items listed below
is preferable.

Enchants and gem selection:
Enchants are basically the same as in affliction, although one might fix +40 spelldamage over soulfrost because of Immolate. In any case, the difference will not be noticed, it's up to personal preference. For gems, you want anything to maintain 202 spell hit.

In addition to what Clix already has posted here, I would like to point out that though shadow damage is what you in most situations will use rather then fire, it is good to keep your fire damage up to a reasonable level as well in the events of a fire mage rather than a spriest would be in the raid group. But shadow damage is definitely your main goal to achieve lots of, but that doesn't necessarily mean that your fire damage should be at a low level like 600ish while your shadow damage is alot higher. So choose your gear wisely, and try to maintain your fire damage a bit up as well if possible. It will also (as clix mentioned) keep up some good damage each time you re-apply immolate to a target, as well as when you throw a conflagerate - if you are a destro lock - when immolate almost is done ticking (which will give some good burst, especially if your shadow bolt is on it's way to the target at the same time you tap conflag. That is like instantly 3,1k - 4k damage non-crit and maybe 6-8k damage if you crit on both) on the target. Besides, if you have BOTH a spriest and a fire mage in the group, and both players are applying increased fire and shadow damage, it can prove to be quite nice to have your fire damage up high. This mainly concerns destro locks, as affliction locks close to never use fire spells.