This is how i used to build warwick, i would start with saying that your build ALWAYS should adapt to your opponents! That is what i can recommend. When i play a champion i rarely build them the same way.

Please don't flame if you look through this build, i made it to help my friend, who just started playing the game and loves WW.

I'm not gonna say much about anything in this build since DEWO's build pretty much says it all and i don't think we need another copy-cat ;)

When jungling make sure to get buffs+dragon as much as possible + getting your team the dragon, this can lead to victory in many cases. Also to gank lanes when ever possible.

My item build is long but it's the order i recommend.
Depending on how the game goes and how you are doing jungling/ganking you can change the build easily. Building black cleaver is also highly recommended.

Hope it helps, if you got questions please leave a comment :)