General info about warlock

Warlock Races
Orc - Blood Fury and the increased pet damage combine to make the Orc perhaps the best Warlock race. the decreased stun duration is nice for PvP and we can ignore the increased damage with axes.

Undead - Underwater Breathing is nice for some quests, especially once you hit Northrend, but nothing a cheap potion can't handle. Will of the Forsaken is a nice PvP skill. Cannibalize is useful when you just have to rub it in to that other player you killed. Maybe that's good enough reason to go Undead.

Blood Elf - Arcane Torrent is a nice spell interrupt with some PvP utility, but otherwise? Well ok, they look good. A truly devastatng Warlock Ability. Really.

Human - The Human Diplomacy skill will allow for more rapid faction gain and the escape ability is nice for PvP, as is the Stealth Detection. Maces, Swords, and a Spirit increase? Who cares? Go Human if you want to waste less time gaining faction.

Gnome - Escape artist is very nice for PvP, as is their small size, and any caster can use an Int bonus, but otherwise? Go Gnome if you want the increased mana pool and the increased Engie skill.

Tradeskills
As with all caster classes, tailoring is the way to go, it’s just impossible to pass up on the massive gear upgrades available by the set-item cloth armor craftable at high levels, many would even rank it higher than a lot of raiding gear.

Enchanting is a very expensive profession to level up, but you can disenchant the goods you make through Tailoring, and use or sell the parts, saving you considerable gold. So those two professions work well together.

Even so, you better have a good gold stash before starting those two professions or good money making skills. If you don't have either then consider waiting till nearly 80, when you have your mounts, before working these professions.

Additionally, a commonly sought combination with tailoring is either one of the three gathering, and thus money making professions – Mining, Skinning, and Herbalism.

All of the Crafting professions, except Blacksmithing, have their uses, but they are also all expensive to level.

Cooking is a good profession to take, partly for the healing foods (even if you're undead,) but more for the buffing foods you will be able to create.

First Aid is a handy skill for those times when you just didn't quite drain enough life.