A few just general tips to add:
Keep UA up on everyone in 3s always so when your mage's frost nova (and frost bomb if he uses it, lately I've used nether tempest and it has been working out great with my boomkin partner so if he uses nether tempest then it doesn't really matter if you cover it with your UA) is dispelled it just applies more pressure. It is probably a good idea in 2s also for if your druid entangles melee often at all. In 3s you really need to make sure someone is feared about 90% of the time, recasting fear right after it goes off and continually fake casting it until it is dispelled (unless your enemies aren't quite up to the skill level of fast dispels or they fear too much for the UA silence) is a really good habit to get into.
The above is just really easy stuff to get into, but stuff you should get in the habit of no matter what anyways. The real thing that I would suggest is getting a few addons, the thing is getting all these at once will be overwhelming so it is up to you to slowly add them in if you can get use out of them, I just know once I started using the last few I downloaded I got about a 100-200 rating increase to put me at rank 40ish in our 2s bracket (just started a 3s team so we haven't made a ton of progress there, also our battle group is rather tiny).
*Diminishing Returns Tracker (to see diminishing returns on your fears).
DBM-Spell Timers (so you can set your partner's defensive cooldowns, offensive cooldowns, and mana cooldowns to show on a DBM countdown so you can always know when they have stuff up).
*GladiatorlosSA along with SpellAlerter so SpellAlerter will tell you who is casting what on who (except for focus target casts), and even if you aren't paying attention to it 100% of the time, you can make GladiatorlosSA scream at you when people pop cooldowns and stuff.
*Gladius is an obvious arena requirement for most people because being able to know when trinkets are down on your enemies is a must, as well as helping you track your CC's a bit better.
*InterruptBar will just help you to dodge interrupts much better and to keep track of when they're on cooldown, although as a warlock if you have
Kil'jaeden's Cunning you will probably need a stopcast keybind that you can use to fake cast people because you can't just move to stop your cast.
LoseControl will just let you keep track of which specific CC's are on your teammates and enemies, and after a match you can go and look back and see who broke which CC's how because it spams your chat area quite a bit over the course of an arena match (if you want) telling what ability from who broke which CC.
For the above addons, the ones with * are the most important IMO for you, but if something doesn't work for you don't worry about getting it.
Sorry if that is a lot, and if you weren't even looking for addons at all, but I can't give too much spectacular warlock advice because I have seen next to no warlocks the past month, so this is what I can help with.
Edited by Mit213, 22 January 2013 - 11:33 PM.