So you might be wondering, "why go top with Warwick?" Well,
Pros

• Eternal Thirst gives you great sustain and a lot of tankiness.
• Hungering Strike gives you a great harass.
• Warwick doesn't have an AoE. This makes his jungle clear times pretty bad in the new jungle. Thus, he works best solo top.
• Infinite Duress Ignite Hungering Strike under turret = instant kill on anybody except Olaf.

Cons

• Renekton
• Olaf
• Too stronk
• Only one really good skin
• You have to remember to toggle Blood Scent so that people don't know when you're coming.
• Infinite Duress can put you in a really bad place.

A lot of 9/21/0 masteries will work. Some particular pieces are optimal.
Initiator - You want this. it works well with Blood Scent
Enlightenment - This and Spirit Visage will put your ulti CD at around 60 seconds.
Other than that, an AD offensive page is best with this build, but an AP offensive page is 100% viable.

Reasoning
Frozen Mallet - Basically a never-ending red buff. Nobody can escape you if you get them below 50% health if you have this.
Frozen Heart - If your team doesn't have a real tank, and the enemy team has a lot of autoattack damage, this and a Thornmail will shut down enemy ad carries.
Bloodthirster - If you are your team's hardest carry, this and a frozen mallet will increase your damage output and your sustain.
Atma's Impaler - If your support already has a Frozen Heart, but your team lacks a true tank, this and either a Frozen Mallet or a second Warmog's Armor will both give you more damage and more durability.
Madred's Bloodrazor - Goes well with a Bloodthirster.
Thornmail - Again, this and a Frozen Heart will make you a seriously tanky bastard.
Phantom Dancer - This goes well with Blood Scent, take this with an Infinity Edge, and have crits fer dayz.
Last Whisper - Armor penetration goes well with a Bloodthirster if you need to go through a tanky opponent like butter.
Infinity Edge - Goes well with either an Atma's Impaler or a Phantom Dancer.