First off, I think warwick is one of better situational team hero and an also a force to reckon with when fighting 1v1.
Depending how you want to play warwick, my guide is not for you. This guide is strictly for aggressive game play. Like tower diving and doing damage. I'd like to start off with Warwicks runebook and masteries because before you even get to the game play you want to start off on the right foot.
Im a fan of tower diving and aggro play. Defense is incredible just that. I usually go 21 Defense 8 Attack and 1 Utility.
Attack: 1 Cripple, 3 Deadliness, 4 Alacrity
Defense: 2 Resistance, 3 Hardiness, 4 Evasion, 1 Nimbleness, 3 Harden skin, 4 Veteran Scar, 3 Ardor, 1 Tenacity.
Utility: 1 Ghost walk.
2 Spell I use are ghost walk and cripple and the situational smite.
Runes: Red slots = desolation. Deso is 1:1 for damage. This will increase the damage you deal to heros and neutral creeps by a flat 20 damage. Yellow = Dodge, for tower dive. Which ever you want for blue book.
Now to the game play. This is exactly how I play my warwick. I get boots 2 health pots and 1 mana at lvl 1. I 3 man Lizard, and first blood mid or top. Engage with a ghost walk lands a slow then cripple to get extra damage. I'm an incredible farmer so I can usually get a witsend by 9-12 minutes and go gank constantly with lizard buff. The ult does about 600 damage at lvl 6 with the lizard buff and witsend. You roam, gank, farm and push towers all game. Then youre good.
Witsend - optional depending on hero makes up. (anti jax, anti judicator)
Bloodthirster or phantom, situational.
Guardian angel or mallet, situational.
Too tired to continue. Ill add more details later.