Depends on whether you are Horde or Alliance - Alliance learn them from their trainer in the Slaughtered Lamb in Stormwind or you can get an imp in Northshire after the quest 'The Stolen Tomb', or in the 'bad area' of Iron Forge. Horde, the trainer in Undercity or Ogrimaar.
Undead.
You get pets :)
The most evil class, in my opinion, is the Warlock because you can be a Demonology Warlock and a Destruction Warlock.
The warlock
Just choose "warlock" under the character selection menu. Well first of all you should of put how can you be a warlock in world of warcraft that question is very misleading
Incinerate can be learned at level 64.
One can find a guide on World of Warcraft warlock PvP builds on noxxic dot com. Additional information can be found on wowhead dot com and wowwiki dot com.
Sabrie, Deathshadow, Deathlock, Shadowmaster, Shadowlock
In popular culture, a warlock is a male witch.
Warlocks can only use cloth armor, nothing else.
In the World of Warcraft gaming franchise and world, there are specific warlock builds that contain demonology, destruction, and affliction. These are found after the 5.0 build of the game.
The warlock cannot lose his/her dreadsteed no matter what, even if you delete it on purpouse you can still get it again.