Maybe you were afk during champion select and you randomly got warwick, The problem is, that you have never played warwick before and you have no clue what you are doing. Upon discovering this you alt tab out and go on mobafire to look up a guide, but you dont have time to read a whole guide during the loading screen. Well here is everything you need to know to do well with warwick.

1. Farm as well as you can and follow the items from above.
2. Conserve your mana, get blue when its available to you.
3. Max - Q FIRST
E SECOND
W LAST
R WHENEVER POSSIBLE
4. Ult onto their carry in teamfights, kill them, win game.

Most people like to jungle warwick, but I feel that he is a lot more fun in the lane. He has great sustainability with his passive and his q, which makes him hard to lane against. He can quickly jump on people with his ult, then a q two secure a kill before they even know what happened.

-Flash is a great getaway spell, allowing you to do many things you cant do with ghost. It can also be used to double jump with your ult which is nice.
-Ignite is great to finish people off especially at the early levels when you cant finish the chase because you dont have your E leveled all the way up.

Other summoner spells-
-Exhaust can be used in place of ignite. Exhaust is great because it can slow an enemy in a chase so you can catch up and get the killing blow. It can also be used in escapes very effectivly. Also in close 1v1 situations the 70% damage reduction can give you an easy win vs someone like Yi or Trynd.

-I like to start with boots and three health pots. This gives you good mobility for last hits. The health pots are good because lanewick cant lifesteal back to full in the early levels. Try to stay in lane until you have enough for your sorcerers boots and some (if not all) of your spirit visage.
-Next you are going to want to get wit's end and the frozen mallet. If you want the attack speed and magic resist first buy wit's end, if you want more health and the slow from your attacks buy the frozen mallet first.
-Your next item is madred's bloodrazor, you should know why.
-After that I would recommend a guardian angel. It is a great item because if the enemy team focuses you, than they didn't focus your carrys, and it doesn't matter because they cant actually kill you right away. By the time you are resurrected by the guardian angel the other team will all be dead, or you will clean then up.

The skill sequence for lanewick is pretty obvious. Q first because it will heal you up in lane and it does a ton of damage. Next is E because it is great for chasing your enemies down. W last because you only need one rank of it for it to be effective. And of course your amazing ult whenever you get the chance.

-In team fights with warwick you want to be on the enemies carries. Even if they end up escaping, you did your job because they were not doing their job dealing damage to your team.

-Warwicks ult is great for initiating/picking off enemy champs. When ashe comes a little to close to fire off a volley, ult onto her (and with your teams help) kill her instantly. Since the other team has just lost their AD carry they will do one of three things.
-ONE: They all turn around and run away, giving you a chance to pick off stragglers or return to your base to buy/heal, or maybe even get a dragon.
-TWO: They enemy team will instantly engage on you, this can be a good thing because they are already down 4v5 and they are missing their carry. If your team is good they should be able to come out on top and push.
-THREE: (Probably the best thing that can happen) Only some of the enemy team will engage giving you two or three free kills (and hopefully no deaths). Now you have a huge advantage and you can dragon or barron.

In conclusion, Warwick is very strong in the lane, he is also very good in teamfights with his suppressing ult, stopping the enemy carries from doing anything. He also has very good chasing ability with his E. Do your job by stopping the carries from doing theirs.