Mobility and tankyness is key. Get up in anyones face and **** them up.
Olaf is insane in solo lane, the trade with Reckless Swing is unreal and when he is strong enough to try and kill he will succeed since the true damage nuke is roflstomp and the constant slow and high damage from Undertow is op. If they would choose to stay nd fight your W will stomp them.

Standard armor for your lane, mr/lvl for mid game and arpen for sustained damage.
Now hpreg quints are key to playing Olaf since they allow you to spam reckless swing like a baws. If you do not have hpreg quints your lane will be hard as hell (especially if facing high sustin champs).

Still experimenting with masteries as they are quite new as of 19/11/11.

I have had the most success with defense/utility since you get so much tankyness and movementspeed.
Offense is pretty useless since you dont crit like someone like vayne.
Your main damage output is reckless swing throughout the entire game and the more time you have to spam true damage the better.
Utility worked okay but not as good as defense as they give kinde of the same pressense with defense being stronger.

I almost never go anything else than the build above since the tankydps meta game.
These items make you almost unkillable, I have done many 1v4 quadkills with this build.

True damage > anything
Sometimes I skill up W over undertow if they are more likley to stay and fight > running.
If I face a range I skill up undertow to rape them from behind like a true viking.

Ghost is awesome combined with your ult, allows you to ran past the entire enemy team and crush the carrys ( most ppl **** their pants when they see and olaf blowing everything at once and charge them ).
Surge is really strong on Olaf. 40 % atkspeed for 12 sec WOW! Combined with the passive and trinforce you max out atkspeed like a baws.
Exhaust is also good if you are not sure if you can 1v1 or hit your undertow.
Flash is allways good, can't tell you how many times I've flash/TRUEDAMAGE in ppls face for firstblood.

Olaf rapes anything except high sutain in lane. You can win lane against a counter if you are simply better than thay are and play it smart.

But rambo is the key to Olaf, if you play like a ***** then you lose like a *****.