This is Olaf done right.

Most people would want me to put some kind of exception thing here. Well NO! WHAT DO YOU THINK YOU COULD BUILD BETTER, uh? Then make your own damn guide. Easy get Ruby Crystal for first item, then build Phage, slow won't always proc but it will make you own early. Bezerk Greaves for some attack speed and movement speed. Followed by finishing Phage into Frozen Mallet. Nothing can escape pretty much at this point. Warmogs for more dmg and health. Then atma's for more dmg and armor. Then Zeke's Herald for the health, life steal and cd reduction. Another Warmogs for more dmg. The only exception possable is for the other team to have so much armor that you have to build a last whisper but then again why did you choose olaf when your whole team is ad. Buy an ap champ, ******.

Ghost and Exhaust. The whole reason for spending one point in summoners wrath. USE IT. There is no exceptions here.

Grab Undertow for early ranged slow, then Vicious Strikes to own with, and then Reckless Swing for another ability and more damage output. Grab ult whenever you can. Level Vicious Strikes first which is your bread and butter. Use it! WIN!