I believe Warwick is one of the best junglers in the game. He's able to do massive amounts of damage in addition to his life stealing abilities. If you want a character that can dish out tons of damage while being safe (life stealing saving him), be a great team ganker (post level 6) and just being bad-***, Choose Warwick.

Warwick can be a great laner as well, though I will be talking about jungling only.

Passive -This spell helps Warwick In jungle and it counts as life steal. It's why Warick can jungle and should be jungling.

Q - This spell is Really important and u shouldn't ignore it. It helps you heal a lot and can even save your life at some points of a the game.

W - This spell is kinda support spell too. At low lvls it help u faster jungle. At late game it help all attack speed players and makeing push go faster which helps alot.

E -This is like passive spell it make your movement speed greatly increase. You have to make sure your Blood Scent is deactivated when u are ganking and activate it when u are going to kill then its really important when you are ganking because enemies will see your mark on their characters.

R -This spell is focusing spell its really powerful for focusing 1 person who is most fed (Example: leblanc who is a mage should be focused). It can change game if only 1 dude is fed. And really useful for ganks post level 6!

Pros:
-Fast and reliable jungler
-Lots of health and dps
-Able to lifesteal all day with blue buff
-Great ganker or support stun
-Ultimate is extremely long range
-Catching an enemy is easy with blood scent (Great finisher)
-Easy to focus a fed or dps champ
-He's a wolf

Cons:
-Requires team work when ganking
-Needs great map awareness
-Sometimes can get focused down (Though if they are focusing you down its fine since your kind of a tanky dps)

Standard runes for most jungling characters.

Greater Mark of Desolation- Will help jungling speed, and ganking.

Greater Quintessence of Desolation- Will help jungling speed, and ganking.

Greater Glyph of Alacrity- Improves jungle speed by a fair bit of time + is great for any attack speed situations. Example: Master Yi V.S Warwick 1v1

Greater Seal of Resilience: This isn't a must, but I use these runes for killing those pesky AD carries and for surviving in the jungler.

20- Offense for the attack speed, damage and damage increase to minions which will help your jungling to be fast and reliable.

10- Utility for increased mana/health regen, increase experience and increase duration for buffs.

1) Cloth armor and 2 health pots:
-Great way to help your jungle run smoothly. Some people may disagree with buying 2 health pots, however, I believe that a health pot can save a life for some critical moments or helping a lane when low on health.

2) Madreds blood razer:
-Madreds gives everything a jungler wants, survivability (armor) and damage. The passive is a 15% chance of hitting a minion with 500dmg in which this is great for jungle purposes.

3)Boots (Mercury Threads):
-Must have item to run and gank. Build this into a mercury threads IF NEEDED. If there is a hard CC team (80% of the time), take the Mercury threads, however if not sorcerers boots actually are useful on him. It applies more dmg for your first skill Hungering Strike and increases the life steal as well. Even look at the other builds posted for Warwick:

http://www.mobafire.com/league-of-legends/build/warwick-jungle-king-549#10

4) Frozen mallet:
-This item is the bread and butter for this build. It allows Warwick to be TANKY (Item adds 700 health). The main proc with this is the added slow. By this time, AD carries should be taking the red buff leaving you with less CC (slows), thus the frozen mallet is there to keep enemies near you while still being tanky.

5) Wits End:
-Attack speed + Magic resist (stacks) is a definite plus for this build since to slow (with forzen mallet) you need to basic attack.

6)Stark's Fervor:
-More attack speed and lifesteal which will make you extremely tanky.

7) Banshees Vail:
-This items great if your being focused down too much, thus getting this in earlier levels might be you choice. This item applies a 1 time shield that protects you from 1 ability (recharges every 45s)

All these items are in order of purchase, however, this build can be changed to your liking. So please leave a comment or message on what you think I should change.

Last hitting with Warwick is a breeze. His melee damage has high damage giving himself an easier time to last hit in laning. His Q is just great for last hitting and life stealing as well making him sustained in jungle/lane.

Please check this guide:

http://www.mobafire.com/league-of-legends/build/warwick-jungle-king-549#10

Or instead of looking throughthe guide, follow this youtube video guide from StoneWall.

http://www.youtube.com/watch?v=eyzdLOv7rwQ

This is my very first build, so don't hate on me too much :). I like to respond to questions and would like feedback for fixing this build up. Try the build, if it doesn't work once, then try again. I've done fairly well with Warwick after using this build several times.

UNDER CONSTRUCTION