This is my very first build. It's not perfect and i havent polished it so much. Anyhow, this is how i play Warwick. Note that this is NOT a jungling build. This build focuses on Attack Damage, Attack speed and some Armor Penetration.

I start off with a pair of Boots 2x health pots and and mana pot. Dont go back untill you can afford Berserker Greaves, greatest would be if you could get the Zeal. After you have gotten the Zeal you are going to save to the Last Whisper. once you have the Last Whisper you should be able to deal some damage. Then the rest is simple. Phantom Dancer > The Bloodthirster > The Black Cleaver > Wit's End.

The summoner abilities is really a personal Preference, some like using heal som like using Ignite.

For Warwick i use Exhaust. Mainly for chasing purposes but also for defensive purposes. Say Master yi is coming to attack you when you are low on HP. You start to run away, he pops his ulti and chases you down. You use Exhaust on him and his attack damage is reduced by 70%. You can now run safely to you teams tower (Almost).

I also use Ignite. If you havent figured out or cant read, you use it to help nuke down a player or to finish off a running champion.

This concludes my build. Please leave comments and rate it. Like i said in the start of this guide/build, this is my very first build and i would appriciate some feedback.