Warwick is an awesome champion. He is also the games strongest jungler. With his natural lifesteal and abilities renewing his health, all you really need to do is give him some longevity in a fight. Many other Warwick players would be looking at this build going what an idiot, WW isnt a tank. But they are wrong. WW is an awesome initiator to teamfights with his ultimate stun. Most builds make him either too squishy or not enough attack damage to really give him longevity with lifesteal items. And he is extremely prone to concentrated attacks and very susceptible if stunned. Giving him more tanky qualities through masteries, items and runes, makes him much harder to kill and will frustrate your opponents and make your team very happy. Also, I only donate two item spots to health items, because thats all you need with a natural lifestealer!
My build incorporates the Jungle King build of DEWO, and gives you the option of jungling, hence the smite skill, till you have your Bloodrazor. Without this, you are a useless rabid dog. Your ultimate will not get you many kills with this build, but will make your enemies hate you for getting them ganked :)
Firstly, LVL in jungle till you are ultimate lvl, 6+, then get yourself your razor and some ninja tabi next. Lane till you have the gold for madreds bloodrazor, but keep an eye on the health of enemy champs in other lanes. If they are low and pressing forward too much, announce your intentions to gank and head on over there. Teleport allows you to switch lanes often and surprise enemy champs often as well. Try to get the weaker champ first, by that i mean either healthwise or type wise (dont ever attack a tank first in a team fight, you will be called a noob among other things...) and sometimes, if they are low enough health, you can pull off a double gank at low levels, with the help of chat friendly teammates. MAke sure they are in position when you ult from the bushes, cos its all for nothing if they are too far away, dont help, or worse, chase him away. I get so angry sometimes cos i coulda got a kill if the my team hadnt chased the bugger away.
Keep laning, and ganking if you can, till you can buy your bloodrazor, makes jungling a breeze, and take on the dragon every chance you get, you need the gold. Now spend your gold on two giants belts, you should now be the hardest to kill on your team. With your new improved health, and your abilities providing all the lifesteal you need, you can initiate team fights, stay to the finish and come out relatively unharmed. This means less time dead, more time laning/jungling/ganking/assists, whatever gets you gold.
Turn your giants belts into a sunfire first, prioritise for a reason, gives you added health, armour, and magic damage to nearby enemies, jungling ridiculous by now, could probly solo the baron if you really wanted to. Next the frozen mallet. With this you can quite easily chase down lone champions. Initiate with ultimate from bushes, hungering strike them below 50% health, with blood scent turned on keep hitting them and the mallet should be slowing them, they cant get away now :D. Your second hungering strike should finish them, and this is a good idea to get back some health, if you lost any, because the other champs could be coming to help. The idea is to be everywhere at once, and jungle while moving between lanes (if teleport is on CD), flashing out and ganking so quick that the other champs have no time to respond before your gone and ganking again.
If things are going well you should be initiating all the team fights by now, and helping them push lanes. With your last bit of gold in the dying moments of the game, enemy team is probably considering surrender, go buy a wits end, if fighting lots of casters, or a last whisper, if fighting tanks and such. Lastly, to make your ultimate even more effective and let you gank more effectively, get a black cleaver. Lowers your targets armour, better damage and will make you quite happy cos you've bought all the items you need! Dont buy a BF sword too early in the game! You need the health not the damage. Preventing ganks from not dying is almost as good as getting them really, if your smart enough to comprehend tactics and warfare strategies.
Being hard to kill will pay off. Your teammates and you, for your assists and jungling, will have a huge gold advantage and probably a LVL advantage too, need i say more? Dont forget to keep an eye on the other lanes, type often, safely, and let your team know what you are doing. Organise ganks. Be the leader. Taking all the hits will get everyone rallied around you and make your team unstoppable.... or legendary if you will :D
GL and HF everyone.