This is an Olaf build, reborn from the ashes to help you master The Berseker .
This build is still under construction, so changes might be made. If you want, leave a comment below.

On an uncharted continent beyond Valoran's grasping clutches, the conqueror named Olaf was born to a long tradition of soldiers unlike most others. Berserkers, as they tout themselves, are warriors who channel fury deep from their cores, unleashing pure and savage wrath upon their enemies. This fearsome evolution is a product of their unforgiving home, Lokfar - a barren tundra where all creatures must vie bitterly for every resource. Olaf belonged to a seafaring clan known for ruthlessly pillaging any and all villages within reach of their dragon-crested longboats. The last time he saw his icy home, Olaf was embarking on an expedition to pioneer and plunder a distant land known only to legend. However, while underway, a terrible storm sprung up and Olaf and his crew were thrown to the mercy of a roiling and pitiless sea.

His ship destroyed, his crew nowhere to be found, Olaf miraculously washed up untold miles from ''friendly'' waters on the foreign shores of Valoran, south of Demacia. This unfamiliar place stunned and frightened the Berserker, for Lokfar is not privy to such potent magicians. Approaching them, Olaf hoped that they could use their mysterious powers to send him back to his people. A bargain was struck. Olaf would use his awesome prowess as a warrior to serve the unusual wars of Valoran in the League of Legends, and in exchange the sorcerers would find him a way to return. Despite his participation in the League, Olaf knows better than to trust the ''finger wagglers'' that run the Institute of War. He deliberately keeps details of his life and home from them. After all, with enough information, they would most certainly find the Lokfarians and dominate them as they have dominated all of Valoran, keeping both quietly -- and unwittingly -- in their thrall.

Beware the war cry of the Berserker. What surges toward you is unyielding, free from the shackles of reason.

So, to start the description my friends I'll talk 'bout runes.

Marks

Greater Mark of Desolation - the best choice, as it goes very well with Olaf's Ultimate and his Armor Penetration capabilities. With these and a Lvl 3 Ultimate you'll cut through their armor like it's cheese.(yum, cheese)

Seals

Greater Seal of Health - good for early game fights and in Reckless Swing. Later they are pretty useless but i don't have any better idea (maybe armor seals) .

Glyphs

Greater Glyph of Cooldown Reduction - great for Olaf. They give you early spammable attacks, as his skill aren't so mana draining. If you have mana problems, get pots or lane with Soraka :D

Quintessences

Greater Quintessence of Attack Damage - a "must-have" because attack damage is the base stat for this champ. I pick this instead of Fortitude because in this build the items and seals are enough.

21/0/9 owns because of high damage dealing and some support masteries . I didn't put the points in defense because the items and runes already give you enough resistance. Remember you are not a tank. You are a fighter with a good quantity of health.

Berserker's Inventory of Winning

Doran's Blade - for a good early game damage output. If you need health instead of damage, get Doran's Shield.


Mercury's Treads or
Berserker's Greaves - Get Berserker's for fast pushing and killing enemies (also use the W ability). If the enemies have high magic damage and/or serious CC champs get Mercury's Treads instead.


Frozen Mallet - An early good item. It gives you some AD but lots of health and a slow passive on-hit effect. Slow an enemy with Q then get to him and continuously slow him down with attacks, W-s and E-s.


Warmog's Armor - The Great Health Item ! After getting this your health will increase dramatically.


Atma's Impaler - The armor it gives is pretty useful and the crit might help you too, but the real use of this item is the passive, which is very useful in combination of great HP.


Black Cleaver - Do I have to tell you why? Well the DMG is greatly upgraded due to the AD and attack speed, and their armor will decay when you attack them with your deadly W strikes and you armor penetration and AD.


Youmuu's Ghostblade - A good item to finish with. Important for its AD and Armor Pen. and its Active Ability.


Get Elixir of Fortitude whenever you can, because it will give you a useful amount of health and attack damage. Also, get the Red Buff anytime!




NOTE: DO NOT BUY BOTH BOOTS FROM THE "ITEM PURCHASES" SECTION!!!

BEST:

Exhaust: The enemies that you can't kill can be weakened in combat. Also for chase purposes.

Surge: Use this, your W and your Ultimate and you will make the other players wet their diapers. Afterwards, check your own diaper.

Others:

Ghost: Used to escape or catch a coward enemy.

Heal: If you're new to Olaf use it for the first 3 matches.

No way:

Heal: After the first 3 matches, replace it with something useful.

Cleanse: It's really not very useful for Olaf. The Ultimate Ability is enough.

Olaf is a great champion, even if he's old. He isn't runes dependent or item dependent, but it's a good choice to be careful when buying items and runes if you want to be the best. Also, remember that Olaf is skill dependent, so if you're bad at playing him, you should get another champ with a different play style.
That's all i have to say about Olaf for now but I will be updating this periodically. Don't forget to vote&comment.