Pros:
- Frozen Mallet enables vicious
stike give high bonus damage.

- Phantom Dancer & [[Boots of
swiftness]] gives high speed bonus.

- Olaf can escape from stuns with Ragnarok.

- With Undertow you can pick easy low health kills.

Cons:
- Olaf does not have any Gank abilities
if enemies come 1v2 or more.

- It's hard to play Olaf without big farms or kills
in late game.

I use Ghost / Exhaust Spells my self.
- Ghost enables you to run to enemy if they escape,
and then you can put exhaust what slows enemies enough
to pick easy kill on it.

I put 4 attack speed marks and 5 armor penetration marks.
These allow you to hit faster and penetrate the enemy armors,
its good when you use vicious strike so you can regenerate hp faster.

Then 9 Armour seals.
These are useful in early game, but not that useful in late game.

9 Mana gylphs.
If you're using alot of Undertow, Reckless swing combination,
you should use them.

But if not using alot of Undertow and Reckless Swing,
You should use Magic Resist per level runes.

The last one is Speed Quintences.
These allow you to get the enemies if you have your
ghost in cooldown.

What you look on every else Olaf guide they tell you to take Vicious Strike First.
But i think its much better to take the Undertow first.
It slows the enemies, and thats good in early game, if you're in bottom or top lane.
You can pick the kill easily then.
The order of the skills. Ragnarok-> Undertow-> Tough It Out-> Reckless Swing.

When you go to 1v1 fight you should use all skills. In order.
Tough It Out-> Ragnarok-> Undertow-> Reckless Swing

In this order vicious strike gives you the Spell vamp to Undertow and Reckless swing, and Ragnarok gives you big Armour/Magic Resistance plus. So you should get the enemy in the fight.

Items you have:
Bloodthirster,
Infinity Edge,
Last Whisper.
Gives you big Attack damage bonus.
And Phantom Dancer:
Gives you Big speed, Attack speed and Crit. Chance bonus.

If you dont get enough money in the game i think You
should buy Youmuu's Ghostblade instead of Infinity Edge.