Hello there, fellow Warlocks. From level 30 and upwards, this is by far the best lvling guide if you are a warlock.
http://www.wow-pro.com/leveling_guides/james_alliance_leveling_guide_-_chapter_i

Now, to the main point.

Many newbeginner warlocks choose talents as they see them good. Do not do this.
You really need some other things than just "cool" spells and such. The best thing would be http://www.worldofwarcraft.com/info/classes/talent-index/.

Best talent to have points in before level 50 is AFFLICTION.

Your starting to become a better warlock, and as you are, you need gear and better knowledge in how to use your minion properly, aswell as which minion to use.

For tanking before level 50: Voidwalker!
After you hit 50, you would change your talents to DEMONOLOGY and get Felguard, which will help you lvl quicker.


LEVEL 30-40 is probably gonna be the most frustrating to level. You will still be a bit newbeginner at this point, but after level 40, you gain experience in the Warlock class.

Here, Drain Tanking is the thing for you.

Drain Life spell: REPLACE THIS SPELL WITH A MACRO!

/cast [nochanneling:Drain Life] Drain Life

Call the macro DrainL or something. This macro does so that when you click the spell, you will, of course, channel.
If you click the spell while channeling, you wont recast it. You will not recast it before the spell is interrupted or finished. You can therefore spamm the mouse button on the spell, so that at once the spell is interrupted or over, you will start casting it again at once. Do this with Drain Mana and Drain Soul spells too. This is simply done by changing the

"Drain Life" in "/cast [nochanneling:Drain Life] Drain Life" with "Drain Mana" or "Drain Soul".

This is done by;;; You use your Voidwalker to tank. Send your pet in. You need to have talent points in Affliction tree, because you need Siphon Life (http://www.wowhead.com/?spell=18265)

/petattack [nocombat]
/castsequence reset=target/combat Immolate, Siphon Life, Curse of Agony, Corruption

This is a macro you would need to make.
Call it "DoT". It will send your minion into the fight at the same time as you cast immolate. When finished casting immolate, click the macro again, and it will cast Siphon Life, then click agan for CoA, and again for Corruption.

When this is done, you use Life Tap to near full mana, and then you use Drain Life untill the mob is on about 10% HP, then you use Drain Soul. You will have chosen a talent from the affliction tree which makes your Drain Soul spell, if being cast when the mob is dieing, will give you back 15% of your mana. This way, you can manage to kill a mob, with having 100% mana and 100% health left after the match.

In the 40s, continue this way, but here you have Dark Pact, which you should use wisely.
Use your Imp, put it on passive and take mana from it by using Dark Pact. This way you do not have to use Life Tap.


Anyways.
Here is a nice guide on how to level a warlock. This guide will show you what talents to pick, and what minions to use.

http://www.wowwiki.com/Leveling_a_warlock#Levels_30-39

At higher level, from 60-70, you would use Felguard minion. In instances and raids, the best minion to use would be the Succubus or the Felguard due to their high damage. In an instance, if you have Demonology, use Felguard.

If you have DESTRUCTION talent, which is best in PvP and Instances, your choice would be Succubus.
In PvP; Succubus makes the dude you fight fall in love with you, and you can cast for some time before your enemy gets to its feet. This is allso good due to most high lvl instances has Humanoids and not Beasts or any other kinds of mobs as main mob.

I will add more when I come over more.
Thanks.
Chris

I myself have a 70 Lock and I can confirm ANYTHING to do with wow-pro.com is bound to be great guides