First you must get the 2nd lizard along the bushes of his team, or if you prefer even bot in the woods by what is known is that little war in the beginning! : p
When one enters the woods, tock onlyyou have this skill, if not smart and let your friend use! then not be afraid to even ks because olaf feed is very good! use theto kill (2nd skill):)

When you get level 2, instead of buying the http://edge1.mobafire.com/images/ability/olaf-vicious-strikes.png buy the 1º skill http://edge1.mobafire.com/images/ability/olaf-undertow.png. Keep playing his ax on the enemy, why so you can take it slow and if you have a chance to butt heads with him at level 3 use the 2nd skill http://edge1.mobafire.com/images/ability/olaf-vicious-strikes.png, and then 3 and if he tries to tack away use the http://edge1.mobafire.com/images/ability/olaf-undertow.png. do not let him breathe, whenever it can tack his ax, that take much hp if you have it with the appropriate runes. in the case, you take a gank, use his ax in what lies behind and what is in front if you see that you can kill him kill him and then tack on another exhaust that comes behind, if it goes to kill so kill him too.
Another important thing for you to have a strong olaf, stay in the jungle when you can, push your lane and go to jungle, because there's already level 10 for dragon and help you pick your team.
Go to gank bot also to help the team and you also get assistance!