My build, the way i like to play olaf.

The rune choices are the obvious ones, quints and marks for armor pen, and glyphs and seals for health to make your vicious strikes that much better.

I chose these masteries because i like to increase my output of damage, while still adding in some survivability.

I specced in offense up to the armor pen talent, put 3 into health/mana regen in the utility tree, and then put the rest in def.

This part is up to you, i like to always buy my boots first, then buy the last whisper for the 40% armor pen.

I then buy the frozen mallet for the health and the slowing effect, and then the warmog's armor for the health.

If it's a long game and you have enough time to farm enough gold for atma's imapler, then definetly purchase it, the extra damage from your health will really add up.

Then very last is stark's fervor for the armor pen/lifesteal aura.

This is also up to you, i just like to do it in this order because i play 3's and my team ganks bottom off of the start, so undertow helps a lot.

heal and ghost, both for survivability, again this part is up to you!

Just my olaf build that i personally use, and quite frankly do well with.

Hope you enjoyed it ;) Don't forget to vote!