How's it going bro?
I feel like giving you a guide of my Olaf build ive been using for a while.
Olaf is a champ that can be played super tanky yet have very good damage output.
He has amazing steroid abilities that makes him Unique and very Fun to play with.

Reds : Greater Mark of Desolation
Yellows : Greater Seal of Resilience
Blues : 6 Greater Glyph of Shielding + 3 Greater Glyph of Celerity
Quints : Greater Quintessence of Desolation

Why those runes:

A) ArmP Red/Quints Are amazing on Olaf, Giving him good damage early and late.
B) Armor Bro, You need it, You take it.
C) 6 MR/Pl for more MR late, and 3 CDR/pl for that extra CDR you will need for 40% CDR

9/21/0

Olaf already has good steroids, You can build him Tank and still be a huge threat.
Defensive tree gives Olaf alot of great things to give up imho and i prefer it to Offensive

I've tried 21/9/0 + 1/21/8 and i believe 9/21/0 is the best suited for him.

Why the above items you may say?

Olaf CDR/Health/Damage is amazing if you ask me.
Why? Cause your skills at 40% CDR are crazy good.

Your W lasts 6 seconds, If you build 40% CDR it takes it from 12 seconds to 7 seconds
Your Q will be much faster at 6 secs (That's not that important but nice also)
Your E will be about 3-4 seconds at this point throwing that true damage out faster.
Your R will be at about 60 seconds, meaning you will be more useful having that UP.

Ionian Boots of Lucidity : For that CDR we talked about

Frozen Heart: Solid Item Armor+CDR+Mana+Debuff for teamplay

Warmog's Armor: Come on now, Do you need a reason for this item?

Frozen Mallet: Amazing Item for Olaf Health/AD and nearly perma slow on enemies.

Atma's Impaler: Its still viable and a good item to have when your nearly at 4k HP.

Maw Of Malmortius: Dat Item and Olaf. Damn. AD+MR Magic Shield and AD when missing HP.

Ghost + Teleport.

Why?

Ghost:

A) Ghost is amazing on Olaf, Your nearly Ungankable with Ghost and your Ultimate
B) Ghost is amazing at chasing people down too, Since you can slow them with Q.



Teleport:

A) You can get to your lane faster
B) You can Tele/Gank at other lanes if needed.
C) Your a extra threat for other lanes.


Other Summoners spells could be Exhaust or Ignite instead of Teleport

Pros:

A) Crazy Steroids
B) Tanky yet can do great dmg
C) Early and late game threat
D) Cant be CC'ed in Teamfights

Cons:

A) Can be kited if you cant Skillshot
B) Gives you the feeling you cant die
C) Only one CC for teamfights

What you should be doing in team fights.

A) Stick on enemy Carry/Softies and make them feel the pain.
B) Open your ultimate if you CC'ed instantly to keep pressuring
C) Slow the enemies that try to run away so your teamates or you can pick them off
D) Stick with your TEAM.