Welcome to the dark art of the Warlock.

First lets go over the stats:

Hit Rating

This is you chance not to miss. You cant dps if you are shooting at a wall. To avoid this we need to get our hit up to 17% or 446. This can be accomplished with gear, gems and talents. If you spec into Suppression, an affliction talent, you can lower this requirement by 3% and make it so that you only need 368. There are other benifits you can get from shadow priests and Draeni but you can not always count on them being in the raid. This is you most important stat!! That said there is no benefit for getting more that 446 so once you get that stop.
So the numbers to remember are 446 or 368.

Spellpower

This is stat number 2. You will be gaining this from gear, enchants and gems. The more the better!!

Haste and Crit

Haste makes you cast faster and Crit ..... well makes you crit more often. For Affliction and Demo locks Haste is marginally better. For Destruction Crit is better.

Spirit

We now gain 30% of our spirit as Spellpower with Fel Armor. We also gain another 20% from Glyph of Life Tap every time we life tap, which will be often.

Stamina and Intellect

Intellect controls how large our mana pool is, stamina our health pool. Luckily for us Stamina is mana with the joy of Life Tap. So if it comes to a choice, pick Stamina over Intellect on any gear since it will keep you alive and give you mana when needed. But usually these stats are paired on our gear, Win!

So what this translates into for each build is:

55_00_16 Sta=0.0000 Int=0.5641 Spi=1.2500 SP=2.2857 Hit=3.5359 Crit=1.4766 Haste=2.1174
56_00_15 Sta=0.0000 Int=0.5434 Spi=1.2660 SP=2.3051 Hit=3.5423 Crit=1.4784 Haste=2.0663
00_56_15 Sta=0.2864 Int=0.6034 Spi=1.3329 SP=2.0455 Hit=4.2627 Crit=1.3815 Haste=1.5840
00_13_58 Sta=0.0000 Int=0.8232 Spi=0.9316 SP=2.1339 Hit=5.5129 Crit=1.4673 Haste=1.4573
00_18_53 Sta=0.0000 Int=0.6531 Spi=0.9287 SP=2.1192 Hit=5.3954 Crit=1.4179 Haste=1.1847

MP5

No. Dont even think about it.

Gems

Something to keep in mind here is that you DO NOT have to match the socket color, but doing so will get you socket bonuses.
Meta: Chaotic Skyflare Diamond
Red: Runed Cardinal Ruby
Yellow: Reckless Ametrine(haste) Potent Ametrine(Crit)
Blue: Purified Dreadstone till you have 2 for the meta requirement. Then ignore the socket color and gem as if it was yellow
Prismatic: Runed Cardinal Ruby

Spells

I will go over actual rotation in the individual specs. There are a few rules of thumb that you will want to keep in mind.

• Always keep you Spellstone / Firestone active.
• Curse of elements should be active on any boss if there is not a Moonkin or Unholy DK in raid.
• Soulshatter should be keybound on the easiest to hit / largest key on your keyboard.

Talent Specs

• Affliction
• Demonology
• Destruction

Addons

SpellPriority

Links

The Warlock's Den - A great site for warlocks by warlocks.
Elitist Jerks - Well they are leet...and jerks. Tons of indepth stat discusion
FelFire - A new Warlock blog that I believe has promise.

Leveling

I've had lots of request for leveling stuff lately so her are some links to the guides at wow.com
Levels 1-20
Levels 21-40
Levels 41-60
Levels 61-70
Levels 71-80