basics of 2v2 for a lock is to chain fear the healer or most annoying class, then DoT both targets.
Druids are MOST important to CC, their heals are so imbal you will not be able to kill anything if the druid is running around.
rogues, because they are the warlocks worst enemy, are 2nd priority, however they are usually very hard to fear, due to their skills which seem built to kill warlocks, so IF you can get a good fear or 2 off on the rogue, do so.
warriors - dont even bother. they have 2 or 3 fear immune abilities, and will just charge you every time.
hunters - only before they enrage, otherwise wait till its over.
other classes are fairly easy to take care of.
CoA, corruption and siphon life the feared target, then DoT up the other target, but try to keep the 1st feared untill DR reduces it below 2 seconds or so.
if you have a warrior of rogue on you, CoE or DeathCoil them. it is very important to get them out of your face, as both these classes can burst you down very fast. (eg drain tanking them wont work very well)
I find that mana drain is not strong enough to be useful in the slightest in 2v2, as any class who wont go down through CC or pure dps will have too much mana for you to effectivley drain, however, if it is a long fight, it may be useful once a mana dependent class ie. druid or priest is under 40%(ish)mana.
when you are not DoTing or fearing someone, Life Drain is the way to go. It has okish dps, but it keeps you at max health.
At the end of a 2v2 fight, i usually come out with 10-13k heals (including healthstone), with means they pretty much have to kill me twice over, which as a lock is what you want - to outlast them (sl/sl dps isnt great, but you are hard to kill, so i suggest a dps or hybrid class to partner with)
IMPORTANT TIPS - if they have a holy/disc priest who casts prayer of mending, dont DoT them, as they will get healed for 800+ every DoT tick (up to 5 DoT ticks)
-Keep your Felpuppy on the healer or a casting class (not very effective vs druids though) at all times
-Use the 'devour magic' ability from the felpuppy at opportune moments, eg. when you or your partner gets sheeped.
-You can summon a voidwalker at the start (no ss or mana cost) and sacrifice it about 8 secs before the game starts (to summon felpuppy and mount) which gives you free shield for about 10-15 secs ( not really useful unless you enjoy charging the opposition)
Hope this helps