Hello, I have not been playing WW for very long but I realized that there are some really bad Wicks out there and I wanted to help with that.
Me and Warwick started out great and i fell for him immediately because of his ability to gank with ease at level 6 and up.
So in conclusion I guess i just want to help shed some light on my way of playing WW.

Now I know some people will say "Heal man your a noob!" but it is a great asset to a ganker to save teammates lives for example, your sitting in a bush waiting to gank and your teammate has low health you can quickly R then heal and in doing so saving your teammate's life.
Ghost is pretty obvious but another choice you could use would be flash, now these would be used for chasing/turret diving or the complete opposite, running away.

Doran's blade:I chose this because of the health life steal and attack damage, another choice would be a vampiric scepter.

Madreds The reason I chose these before boots was because of the attack damage and attack speed which in all honesty provide you with more lane survival because of your life steal and life steal passive also they have a passive which allows you to nuke through high health champions like dr mundo. If you the other team does not have a high health champion or a tank with over 3k health i suggest getting a phantom dancer instead for the crit and high attack speed.

Berserker's greaves: Another option would be boots of swiftness if you want to go really fast just for lols.

Trin force: The reason I get this is because if you haven't noticed you go OOM quite a bit on warwick this will help with that and the passive from the phage to slow your foes and add to your survivability.

Infinity edge: Damage and and crit with one of the best passives... enough said

Bloodthirster: Replace your Doran's blade with a bf sword if you cant by the whole thing then if you can afford it then replace your Doran's blade with the bloodthirster, the reason for this is just because its an upgrade to Doran's without the bonus health.

Warmog armor: Just to make it impossible to kill you another option to this is a black cleaver for ultimate damage or a phantom dancer for movement speed and AS

If you happen to get harassed early game and need to B well, if you have even 1/3 of your health kill the small golems by opening with Q fallowed by a W and you should be back to near full health even at early game. This will also help in getting gold.
Now farming on Wick is very simple it just requires you to spam auto attack minions and even at level 4 i go and solo dragon if im near it and the enemy is B or dead.
Also you want to kill the Lizard/ancient golem whenever you can as the buffs really help with ganking and farming.

SIDE NOTE: ALWAYS TOGGLE E OFF WHEN YOUR DOING THE JUNGLE/WAITING FOR A GANK

I start with Q and max it out first because of its awesome damage and heal.
Now W is next for maxing out because of its attack speed bonus, enough said.
E now this we grab this third because it helps you finish off fleeing enemies.
R this is the ultimate ganking ability because it stuns and does some crazy damage with its attack speed increase, this will always be used to open on people unless you have less that half health then you can open with Q then ulti his ***!

Now i haven't seen anyone make a ganking section and I know it was always something I wanted in a guide so here we go.
Now first thing first disable E and sit in a bush, wait until either your enemy is over extended or has low enough health that you can stun and q to finish off.

Your basic rotation for a basic over extended enemy is R W Q then toggle E back on to get them if they flash or pop ghost.