Scare-wick is actually great to lane with but most people just use him as a jungler. He has great sustain thanks to his passive Eternal Thirst. Warwick by level 3 can haunt most enemies. Last hitting is not a problem with warwick and you can always jungle if you need some some gold.
Nothing much to stress on Masteries because i believe you should decide what Masteries you want but whats up there is what should be if you follow the build.
1st Build - AS
Boots of Speed with 3 Health Potion is a good starter item making you harder to kill, more mobile, able to last hit better and just move around and dodge skill shots if there was any to dodge.
Zeal and Boots of Speed complement each other well early game making you very mobile to do ganks or just jungle.
Madred's Bloodrazor is a must on Warwick seriously ask anybody on the street.
Warmog's Armor should be bought early to get its full effect, +350 health and + 10/5sec health regen.
Phantom Dancer should be completed for more AS, critical strike, and a movement boost.
The Black Cleaver has a good AS and AD as well as its passive which can make killing tanks a breeze.
Ionic Spark is not popular but i think it is a great item 250 health, 50% AS, and its passive is some what AOE.
This guide should be effective if you need a role of an ADS if you can get off a few kills early game and you gain a level advantage you would be doing great later in the game, it is possible to take down a turret at level 6 due to the AS on Warwick. You wouldn't be very tanky but in a 1v1 you should come out victorious 80% of the time. Taking down AP casters would be a breeze unless you get stunned or feared then i would consider retreating.
2nd Build - Tank
Mercury's Treads great magic resistance for early game and tenacity.
Madred's Razors makes killing minions and monsters easy.
Warmog's Armor makes you pretty tanky due to your passive and great sustain.
Tiamat cheap around 2000 gold and gives a good damage of 50 with health and mana regen for spam and lane sustain but can be sold later on to a better item like some type of aura.
Phantom Dancer makes getting around the map easier and chasing champions easier.
Sunfire Cape decent health and armor with a good passive.
Tanky Warwick means you can be taking damage but still do good amount of damage and with the health regen you should be able to heal your self if you are unable to heal from Eternal Thirst. You can be even tankier but you would have to sacrifice your offensive stats.
3rd Build - Immortal
Doran's Shield Armor, Health and Health regen. What more can you ask for?
Mercury's Treads because you wont be getting much defensive item with this build.
Zeal and Vampiric Scepter remember with Greater Quintessence of Life Steal your life steal should be 19% i think.
Phantom Dancer AS and movement
Bilgewater Cutlass 35 AD, 15 Life steal and a nice active with 150 damage and 50% slow for 3 secs its like a free Exhaust with only 60 sec cooldown. By now your life steal is 24%.
Frozen Mallet 700 health, 20 AD, and a slow.
Madred's Bloodrazor must for late game damage especially when you go tank hunting.
Guardian Angel If you die, it must be of old age cas with this you wont die once every 5
This is my personal favorite build and be sure to try it if you have 3 Greater Quintessence of Life Steal. I think this a hybrid guide and you can jungle with it as well. Its fun to take damage from the enemy champion especially if they are a mage or Ability depended like Irelia take some damage make them *waste their mana and when you think time is right like when you know their abilities are on cooldown initiate the fight and or just keep farming.