This and many other fora get a lot of questions about people trying affliction I thought I would make a small how to with some links and some basic advice.
I am not going into deeper maths, but I will try to link as much to more in depth guides as possible.
The rotation is quite hard and takes a lot of getting used to, practice a lot on the test dummies, but do consider that the test dummy results are not accurate at all!
http://www.wowhead.com/?talent=IfxMbzMAoVq0IstZE00V is currently the template you want to start with. There are 3 more points to spend on your liking we can maybe discuss later about.
I could discuss why you would take everything but you can find that on the provided links.
I will discuss things you don't take.
Frailty, because curse of weakness and curse of recklessness do not stack.
Improved Drain Soul, because they buffed all tanks to do 30% more threat than they were doing in TBC.
Improved Fear, pvp talent.
Fel Concentration, in a raid when you get hit, you're most likely to die anyway, so less pushback doesn't help very much.
Grim Reach, none of the encounters require this skill thusly useless and the points are better spent in talents that actually increases your dps.
Curse of Exhaustion, very little use in raids and doesn't work on raid bosses anyway.
Improved felhunter, the improved fel intelligence is not a real dps improvement and the mana return is useless if you don't use dark pact.
Dark Pact, awesome talent in TBC, terribly weak in wrath, life tap will grant you at least twice the amount of mana per global cooldown and won't drain the mana of your pet, considering you get haunt, siphon life and fel armor heals the life you tap away is easily replenished.
How of Terror, pvp talent.
One thing I see a lot of people do when they spec affliction is forget to take the malediction talent. This talent will not only boost your curse of the elements to have 3% more effect, it will increase all the damage done by you through spells even if you don't use CoE.
I see some people try and spec into the demo tree to reach demonic aegis, even if demonic aegis was worth as much dps as ruin (which is better by far) you have to pass a lot of useless talents like Demonic Embrace and Fel Vitality.
Most people agree that the current best rotation for affliction is:
Shadow Bolt, Haunt, Unstable Affliction, Immolate, Corruption, Curse of Agony, Siphon Life.
Personally, I prefer:
Shadow Bolt, Haunt, Corruption, Siphon Life, Curse of Agony, Unstable Affliction, Immolate.
The order of putting up your DoTs does not make very much of a difference and this comes down to personal preference, but I will analyze the standard rotation for you as following.
You start with a shadow bolt since this is your longest cast you want to get away the first because it applies the shadow embrace debuff and is of a different cast time than all your other DoTs.
Haunt applies your second stack of shadow embrace and more importantly applies a debuff that makes all your DoTs do 20% more damage.
Unstable Affliction and Immolate have the same cast time and duration, therefor you combine both DoT casts to basicly form a block.
Corruption, Curse of Agony and Siphon life are cast thereafter in the sequence.
Why I personally prefer my rotation is that I can cast my shadow bolt + haunt and then cast my instant DoTs so I have 4 seconds of time to position myself further, than comes the block of UA/Immo.
The reason I cast Siphon Life and Curse of Agony in this order is to form a block of Siphon Life and glyphed Curse of Agony which have a duration of 30 and 28 seconds devided by one global cooldown (1.5 second without calculating haste).
Below 25% health of your target you will want to drop immolate and shadow bolt and use your drain soul which gets boosted by your death's embrace by 12% and does 4 times as much damage when the target is below 25% health.
Immolate is a destruction spell and is NOT classified as a DoT but a direct damage spell (DD) and it does not effect your soul siphon.
You do however cast your immolate spell because it's damage per cast time (DPCT) is higher than that of a shadow bolt (your filler spell), even when you would have 100% crit.
Shadow Bolt filler
Your filler spell, opposed to TBC content when people specced 21/40 to spam shadow bolts the spell actually got really weak but it is still a better source of damage than anything else when all your DoTs are ticking.
Drain Life filler?
Drain Life is an affliction talent and benefits from soul siphon which you would likely suspect to be a good filler spell. HOWEVER the drain life spell gets a damage penalty since it does damage AND heals you at the same time.
It also does less damage than a totally untalented 3 second cast non-critting shadow bolt and thusly can be written off from any proper rotation.
Range and threat reduction talents
In the current content it is not needed to have any talent that would require you to be any further than the maximum distance you can be at, even more so it would require you to take up both range talents from the affliction AND the destruction trees with which you lose 4 valuable talents point you could be spending on talents to improve your current dps.
The same applies for threat reduction talents, as I have said before tanks are doing 30% more threat and unless you have points left from suppresion because you are hit capped from your gear they serve no use and than even still would be better spent in talents that improve your dps because if a tank isn't holding aggro he is as useless as he can be.
A talent that has a diminishing return on talent points spent.
What that means is that every talent point you put in it has less value than the point you have put into it before.
I myself however really like this talent and even though on paper it may not look as good as it does it does mean when movement is involved in a fight you have more chance to proc this talent and start your rotation again if any of your DoTs have fallen off.
I therefore spend full 3 points in the talent.
A talent that absolutely seems completely useless in affliction because we only have one fire spell in it. But the thing is that this fire spell just scales insanely well and considering this talent procs on all shadow spell and we have a lot of them ticking on a target it procs a lot and makes your immolate do 10% more damage which boosts it's DPCT even further.
A talent where I am somewhat in doubt about. It gives you 1% more hit rating on your destruction spells (shadow bolt and immolate) but if you have 14% hit rating on your gear you will hardly if ever miss a shadow bolt or immolate and even if this happens it's loss in dps is not actually that big.
This talent is however open to discussion. Personally I go without.
Calculated has been on Elitist Jerks that the glyphs of Immolate, Siphon Life and Curse of Agony have the biggest impact in dps.
Hit (until hit capped) -> Spell Power -> Haste -> Crit -> Spirit -> intellect.
Spell power is our main stat and make all our DoTs do more damage.
Haste affects our global cooldown, which is triggered by every spell and considering it does not make our DoTs tick any faster we do use a lot of global cooldowns and any time spent waiting for global cooldown is time spent not doing dps.
Crit affects with pandemic our corruption and unstable affliction spell and also the innitial damage of our immolate and of course our shadow bolt fillers.
Spirit affects our total spell power through fel armor by 30% of our total spirit and effects the amount of mana returned through our life tap, though you will most likely not try to gear up specificly for spirit, it comes on a lot of gear and is a nice additional stat to recieve.
Intellect gives us more mana and gives a very slight increase to crit chance, but deemed far inferior to all others stats.
Breakdowns in stats are different for everyone and change when you change gear, therefor I use the following which isn't at all precise, but gives me a rough indicator of the value of gear.
1 Spell Power is worth 1
1 Haste is worth roughly 2/3 of 1 SP
1 Crit is worth roughly 1/3 of 1 SP
A lot of meta gems require to have a certain amount of different coloured gems. I therefor prefer the 25 Spell Power + 2% intellect meta gem because it only requires 3 red gems.
Unless you aren't hit capped the only gems you will want over anything else including almost all socket bonuses are the spell power gems.
Warlocks have a lot of different pets to choose from all range in their utility but most of these we choose for dps.
I'll start with the first demon first.
The imp, has an ability called blood pact which is really nice because it gives you extra health but gets overwritten if you have a warrior in your raid using commanding shout, does very nice untalented dps but still being a caster pet is quite fragile but unfortnuately sometimes the only option to have out as a pet because when he is not attacking you can have him phase shifted which means he gets no damage and you get a nice boost in health.
Voidwalker, tanking pet, is nice for soloing if you choose to use him at all, personally, I find him very weak and choose to mostly just ignore this pet considering he basicly can still be killed in one shot by any raid or heroic mobs/bosses.
The Succubs, a pvp pet, has a channeled charm spell which can keep another player or a mob if they're humanoid crowd controlled for a small period but is deemed fairly unreliable.
The Felhunter, the affliction pet by choice, grants a substantial buff to intelligence and spirit both which provide a small dps boost. With the new patch the scaling of the felhunter is a lot better and should basicly be used at all times when possible.
The infernal, high dps, short life. The Infernal benefits from the constant immolation aura it has and in the last patch as far as I noted did about 800 dps or so and does a small stun on mobs that aren't immune for stuns, this pet however only lives for one minute, choose so only if you think a boss has less than one minute to live or your pet gets killed.
The Doomguard, our heaviest hitting pet. He is a real monster, he looks like one and hits like a freight train. Fully raid buffed the doomguard has 50k health and should do near 1k dps while a felhunter should be doing 350 dps untalented and the imp around 250~300 dps. The problem with the doomguard is however that it only lasts for 15 minutes and has an 1 hour cooldown. If you want the best result on a boss you will want to turn off all his abilities from auto-cast and only let him melee.
To play affliction properly you will need a timer to keep track of your DoTs, I personally recommend Quartz, other addons might include DoT timer, Class Timer or ForteXwarlock.
These links will go deeper into what I have tried to combine into a small and as simple howto as I can provide from my experience.
Edited for pets.