This guide is my idea of how Warwick should be played and how his kit has created his play style. I don't think Warwick has the tools to be an effective tank and shouldn't be treated as such. He is very strong early game and that should be capitalized on. I see him as a blood thirsty, hunting, killing machine that can easily pick off low health enemies allowing you to give your team pressure on objectives and around the map.

Warwick doesn't need a specific buff starting off and has high jungle sustain. He tends to have mana problems out of jungle and early off if you are spamming Q. Personally I always start bottom buff. Blue Path: Blue, Gromp, Scuttle, Wolves, Red, then gank or invade enemy jungle. Red Path: Red, Wolves, Scuttle, Blue, Gank if possible, if not Gromp. If you want to secure an early gank on level 2 you will likely need Primal Howl.

These items are key to this build and needed. Tiamat helps tremendously with Warwick's farming early game and is needed as soon as possible. First off, Skirmisher's helps if you are going up against strong duelists and need the extra boost. Stalker's is strong versus enemies that can easily kite you, but with Warwick's ultimate, Blood Hunt passive and CC from E, it isn't needed. Bloodrazor is my jungle item of choice here because it helps against objectives (dragons/turrets), it also works very well with the rest of the build. Warrior is good if you want to burst enemies early but isn't as effective late game. Cinderhulk doesn't help much at all in my opinion, and makes it more difficult to snowball early which is a key part of Warwick's strength. Ninja's are the primary boots you will want to build because you will be getting enough magic resist from Spirit Voyage + Wit's End. If you want to do massive magic damage early and burst the enemies with Q, Sorcerer Shoes will accomplish.

These are the items I find most effective (listed in order of importance). Guinsoo's Rageblade pairs nicely with Warwick's passive ability since it is on-hit and deal both magic and physical damage. Although, it does not stack on his ultimate, it is still an effective item when taking dragons/turrets. Wit's End is similar in it's ability to shred the enemy and is great combined with Rageblade's/Warwick's passive. Titanic Hydra is a good item to finish after Rageblade because it also has an on-hit passive. Blade of the Ruined King is another on-hit item that isn't as neccesary as the others because life steal items are pretty useless on Warwick since he already heals for the majority of his attacks/abilities, but the on-hit passive makes it worth mentioning. Trinity Force is a well-rounded item for Warwick, and gives him everything that fits into his kit (Attack Speed, Movement Speed, Attack Damage, Health, CDR). Death Dance is primarily for a full damage build, and helps with sustain (bleed passive).

These items are not usually needed unless you are serving as the team's primary tank (Warwick is a better hunter/bruiser than a tank). Nonetheless, Iceborn Gauntlet is a variation to Trinity Force allowing Warwick to get some tankiness while being able to slow down the enemies. Deadman's is one of the better armor options because of it's high amount of armor/health + movement speed. Guardian Angel is always viable option since it grants armor/damage and a strong passive. Frozen Heart and Thornmail are just pure armor options and usually only used against a full AD team.

The other magic resist items are not usually necessary unless other team is full AP, and still should not be needed if with Wit's End + Spirit Voyage

Blood Hunt is the best ability to max first on Warwick because it allows him to move around the map quickly and farm quicker. There are much more benefits to maxing W rather than Q because Q damage only scales based on health so it isn't effective early game maxed than it is late game.

Tips: Secure ganks with activating E, swinging around and enemy with Q and forcing them to flee the other direction. Wariwck's ultimate can have multiple uses, it helps lock down ADC's in teamfights, it can kill low-health champs from escaping, it can be used as an escape in bad situations. In duels, it is best used when you reach low health so you can restore it before possibly dying.

Dark Harvest is the perfect scaling rune to help with Warwick's weakness in the late game. It also helps him snowball early and works with Blood Hunt. Sudden Impact is probably the best option here because it is proc'd on Q hold's as well as his ultimate. I like Eyeball Collection for the snowball + damage. Relentless Hunter is key because it helps with movement speed + ganks.

As for the secondary tree, I have found precision to be more effective than sorcery (Celerity/Gathering Storm/ because Warwick needs the added attack speed. Coup De Grace helps with Dark Harvest as well as Blood Hunt.

Press the Attack and Conquerer can both work as well, but are better used when Warwick is more tanky and sustains longer in team-fights.