Warwick is a tanky jungler with a nice bit of attack damage. His Q (hungering strike) and his passive make him very durable in fights and jungling due to the heal and bonus damage.

In a teamfight or gank i suggest initiating with youre ultimate to keep youre oponent in place so youre team can easily surrond them then i suggest activating youre W and using your Q to lower their health down below 50 percent so you get youre speed boost at this point they wiill likely use flash to get away while they are below 50 percent health you have a speed boost this can be increased with ghost to easily catch up simply get into range to activate hungering strikes on them this will give you timme to catch up and finish them off with basic attacks. (well if they werent dead already)

in jungling you want to go wolves,wraiths,golems,be carefull with buffs the elder lizard buff can counteract youre passive so you may need to use you Q to get red buff. To get the ancient golem simply get a bit of attack speed.

One game (this is true) I was bot and against nidalee. Every time she threw a spear from max range I would dodge. but then i realized I could go farm and she wouldn't max range hit me because then she wasnt able to farm so i simply attacked nidalee and she launched spear after spear directly at me with little affect. Next pvp same lane different nidalee player and the same result no damage taken. So if you get that youre passive can make you take insane amounts of pounding and still not have much health loss its even possible to have health gain.

excellent jungler slightly item dependent
high self regen Q uses large amounts of mana
good base damage starting damage isnt high
high defense