Freakin' Warlocks...

Here we go, time to show you how to play a Warlock.
If you're leveling, Demonology would be the ideal way to go, due to its increased pet power and survivability. Something like this would be a good spec to work to for the WotLK players.

http://talent.mmo-champion.com/?warlock=000000000000000000000000000000320330113521253013503105105203015020000000000000000&glyph=071509030506&version=9626

For PvP, Affliction is just great, it enhances your Damage Over Time spells to the max. Nuff said, people hate DoTs. Here is something I cooked up for the PvP locks out there.

http://talent.mmo-champion.com/?warlock=035000223122351105351230115100300000000000000000000000005230010000000000000000000&glyph=201703010206&version=9626

Now for the good stuff, Warlock Raiding. Destruction is THE raiding spec, it just dishes out the damage. Destruct Locks used to have a choice in Burning Crusade, Fire or Shadow, seeing as you could put points in either direction, but seeing as Warlocks that want the new Chaos Bolt move can't get Demonic Sacrifice anymore, which was a great increase in dmg, I believe fire is better.
Your dps cycle for bosses should be Immolate, Incinerate until you have a couple seconds left on you Immolate DoT then cast Conflagrate. All the while casting Chaos Bolt when its off cooldown. Use Curse of Elements helps you and the whole raid out. Keep your imp out as well.
Here is the Destruction Raid spec I came up with.

http://talent.mmo-champion.com/?warlock=030000000000000000000000000023300030003000000000000000005203205220331051035030351&glyph=021213050206&version=9626