Warwick is a quite viable champion. He can be played in a lot of positions while still being a quite effective champion. Though many people tend to play warwick as a tanky/ap/bruiser so and so. I play him as an AD carry. This is because his skills and passive are very offensive and work very well as a ad champion.

well, the runes i have picked are all flat damage runes. This is because warwick is not very strong early game and can die quite easily. Also, his w and recurve bows make up for the lack of attack speed and so, attack damage will be essential for the early game.

Pros :
warwick is usually a tanky character and if you build warwick like this, the opponents may not expect an adc warwick.
warwick has a lot of sustainability because of his passive and q skill.
grows to be very strong if you can get him to be just a bit fed and can snowball.

Cons :
quite weak early game
cant do much to level ranged carries until level 6
blind will kill you.

very offensive abilities for ad carrying and utilities for the left mastery points.
i think executioner is bad to miss since i am putting a lot into the offensive masteries, but masteries in utility can be switched to defensive.

recurve bow gives you quite a lot of attack speed (40%) and ionic spark and wit's end gives you defensive qualities while also giving you offensive abilities to be able to win most 1 vs 1 fights. the attack speed lets you get on-hit stacks of wit's end and ionic spark faster while giving you an enhancement on your passive of your basic attack. Then after you have a lot of attack speed, getting even a bit of attack damage based items will greatly increase your output of damage. lifesteal helps sustain and survive while fighting even without being tanky. Most of the time, frozen mallet would be better than getting an infinity edge, but if you arent having too much trouble surviving (because of your lifesteal), then infinity edge will give you a boost to damage and rate of healing from lifesteal. although frozen mallet slows the opponent down, warwick's e makes him quite fast and you most likely will not be buying frozen mallet for this effect.

well, since i have flat damage runes, attack speed will increase your damage output quite a bit (w). warwick's w also benefits other teammates and is quite useful in the first fight. q helps sustain while jungling and just when you are low on health and high on mana. e is needed at the start because this allows you to locate where your enemy is when below half health and you get a bonus speed boost (very beneficial). I tend to get my ulti as quick as i can and level that up when i can as it is actually a quite strong skill. w is my priority for pushing, jungling, damage dealing, what ever.

the farming phase is always very very important. if you don't stay near the exp receiving area, you are really bad and it's over. if you cant last hit very well, it's ok, but obviously, it is better to get the cs as this gives you a lot of money over a period of time. never use q to farm as this takes too much mana. you can use it if you are low on health, but dont use q solely to push or last hit, it's a waste. try using your w as much as you can so you can push extensively. If you can do this well, you will push your minions all the way to the opponent's turret and the opponent will receive less exp.this also means less of the opponent's minions will die and therefore, you can get all the minion exp while doing other stuff in the process. this means you also have time to do other things such as ganking, jungling and capturing altars without losing too much exp from being out of lane. I wouldnt gank too early because laning isnt very efficient if you move around too much, but if ganks are absolutely needed, theres no way to avoid that. I start jungling golems at lvl 3 or 4 as wolves and wraiths are too far away and will make you lose time getting back to lane. Also, if you can, try to counter jungle as well but only if it is very safe to do so. If you are jungling golems, if you situate your champion correctly, you can receive minion exp while jungling.