Witch Doctor is a range intelligence support hero. He is famed for his Death Ward ultimate which deals tremendous burst physical damage to nearby enemy heroes which, if combined with his Maledict ability which amplifies damage taken, can often net him solo kills.
Skills
Paralyzing Cask is skilled first but maxed second.
Voodoo Restoration is skilled and maxed last. 1 early point is great for lane regen.
Maledict is skilled and max first.
Death Ward is always skilled (levels 6, 11 and 16).
Items
Starting Items: Courier and/or Observer Wards, Tangos, Healing Salve, 3x Iron Branches, Clarity.
Early Game: Flying Courier, Observer Wards, Boots of Speed, Magic Wand, Bracer.
Core: Arcane Boots, Mekanism.
Luxury Items: Drums of Endurance, Aghanim's Scepter, Black King Bar, Scythe of Vyse, Necronomicon, Dagon, Force Staff, Orchid Malevolence, Shadow Blade.
Situational Items: Sentry Wards, Dust, Gem (vision). Smoke (ganking). Pipe of Insight (if didn't buy the Mek). Boots of Travel (late game). Vladmir's Offering (melee cores).