Warlock is one of the safest solo classes in Vanilla. You put damage-over-time spells on a mob, let your pet hold it, and heal yourself off the damage you are already dealing. You rarely die and you rarely stop to drink.
Leveling: dots and drain
Curse of Agony, Corruption, and Immolate go on the mob, then you Drain Life while they tick. The drain heals you, so a normal fight costs you almost no downtime. When you out-level your soul shard supply, keep a few free for Healthstones and summons rather than burning them all on Soul Fire.
Your pet
- Voidwalker for safety. Its taunt holds the mob and its sacrifice gives you a shield, so a bad pull rarely kills you. Most people level with the Voidwalker.
- Succubus for speed. More damage, less safety. Good once you trust your pulls and want faster kills.
- Imp early on, for the stamina buff and ranged hits, before you have the Voidwalker.
Keep a few shards on you for re-summoning the pet after a death, and for Healthstones, which are free healing you should hand out in every group.
Soul shards
Shards are your currency and they eat bag space. Carry one dedicated soul bag, drain a shard before a fight you might need cooldowns for, and do not hoard a full bag of them. A second profession bag fills up fast if you forget.
At 60
Warlocks raid for two things: damage and curses. You hold a curse slot for the raid, often Curse of Elements to boost everyone’s magic damage, or Curse of Recklessness and Shadow on your own target. The common raid builds run Destruction with Ruin for the big Shadow Bolt crits. You also bring Healthstones, Soulstones to pre-res a healer, and summons for stragglers.
The mount
Warlocks get a free felsteed at low level and an epic dreadsteed from a long quest chain in Dire Maul. The dreadsteed chain needs a group and some reagents, so save it for when you are around 60 and can clear Dire Maul.