Warwick is one of the most competitives solo laners in League Of Legends. Warwick can dominate the lane with this build and he can counter the most of bruisers!

Passive - Eternal Thirst
Each of Warwick's attacks will heal him for 6 Health. The amount restored increases by 6 at levels 7 and 13. Each successive attack against the same target will restore increasing amounts of health to Warwick.
Originally this is what made Warwick a good jungler. Now, this is what makes you a tank. You can solo duel almost any melee champ at any level with this. This sustain can be supplemented with attack speed items or Spirit Visage. By end game, you end up healing almost 50 HP per attack.

Q - Hungering Strike
Strikes an enemy for the greater value between 75/125/175/225/275 (+1) and 8/11/14/17/20% of the target's maximum Health as magic damage (can only do flat damage to monsters), and heals Warwick for ////% of the damage dealt.
Range: 400
Cost: 70/80/90/100/110 Mana
This is your poking/damage output skill. Unfortunately it got nerfed hard after the last patch. It has decent range, so any time an enemy comes close, hit them with an auto attack then a Q. Watch your mana costs, as you will run out fairly quickly early game. First skill i max.

W - Hunters Call
Warwick lets out a howl that inspires all nearby allied champions. This increases Warwick's attack speed by 40/50/60/70/80% and all nearby friendly champions' attack speed by half of that for 10 seconds.
Range: 20
Cost: 35/35/35/35/35 Mana
This is a great source of attack speed early, and acts as a great steroid when your jungler is ganking your lane or when you are in team fights. I alternate this between E, depending on which i need most at the time. If you find yourself in the jungle alot mid game, keep this skill one point ahead of your E. This also allows you to build more damage and health rather than attack speed items. This combo will shut down the enemy team by severely crippling their damage output, while increasing yours.

E - Blood Scent
Toggle: Warwick senses enemy champions under 50% life within 1500/2300/3100/3900/4700 distance of him; while he detects a low-health enemy, he gains 20/25/30/35/40% Movement Speed.
Range: 20
Cost: No Cost
This makes Warwick the hunter. You can chase people around the map like crazy, slowing them down while your team catches up. This can also be good defensively; if the enemy is half health and tries to gank, you will see him in the brush. If you are feeling brave, you may not even need tier 2 boots right away with your E. This is great to have at every point in the game, as it also gives vision of low health enemies. I alternate leveling this and W, depending on the situation. If you find yourself chasing a lot, keep this one point above your W.

R - Infinite Duress
Warwick lunges at an enemy Champion, suppressing his target for 1.7 seconds. While they are suppressed, Warwick quickly strikes the target 5 times for 33% of his Attack Damage plus 40/60/80 as magic damage. Warwick gains an additional 30% Lifesteal while performing Infinite Duress.
Range: 700
Cost: 100/125/150 Mana
This is one of the best Ultimates in the game. With an Immobilization and a heal plus crazy damage scaling after the recent patch (adds 2x bonus AD), everyone will be scared of you as soon as you reach level 6. The recent patch also makes Warwicks ultimate apply on hit effects, including the effects from his recently buffed passive. You will do a ton of burst damage combining this ult with a couple of Qs and an ignite. This is also a great chasing skill, as you can suppress an enemy while your team catches up to finish him off. This skill also works as an initiator; While you maul the piss out of the enemy AD carry, the enemy team will try to kill you even though you are healing a ton, and all the while your team is pounding the enemy into oblivion. Obviously this is maxed when possible, level 6, 11 and 16.