Some Notes:

-Start with Undertow, Max out Reckless Swing (1st) and Vicious Strike (2nd) as soon as possible.
-Start with either Doran's Shield or Vampiric Scepter
- Berserker's Greaves or Mercury Treads , depending on the team.
- Build up a Frozen Mallet, starting off with a Phage.

By this time you should be okay. This will last for about 15-20minutes and then you can have a thorough look into this guide later. THANK ME LATER. ^^

Well I've been in this community for awhile now, maybe almost a year?
After looking at constant builds and learning from others I am now able to know which items to get for who.
I wanted to share with the community some of my builds and I'll be showing you my build/s for one of the fun characters, OLAF.
This will be my first build so be sure to contact me for questions.

I'm the type of Olaf that tends to wanna harass the enemy champions and deal some sufficient damage, but also be able to hold the lane and keep myself from dying.
Thats why I get both armor pen marks and quints, some armor seals, and mana regeneration glyphs.
Armor Pen does great with olaf with his Vicious Strikes along with a Reckless Swing combo.
Mana Regen Glyphs mainly cause your a melee and if your up against range your only way to farm is your Undertow.
The Armor seals are just a little something to reduce them range autos.

TBH, I'm not too good with runes but I always try to fix these up to suit myself, you can always mix it up a little so don't follow my build exactly.

This is my typical Olaf Masteries. I pick up the Cripple and Haste buffs, some Awareness experience gain and Utility Mastery buff duration increase. There's also the Armor penertration and all the other damage increase masteries in there.
Feel free to change it a bit, as it it just my personal opinion.

- For each 1% health lost, Olaf gains 1% attack speed. Pretty self-explanatory. So when you lose health in fights your attack speed becomes crazy fast. Fun passive and might even cost you either a kill or a death.

- Undertow, you throw that axe in a line and deals damage. Picking up the axe reduces the cooldown by 6 seconds. I only get this to level 1 at start because, undertow can get higher damage the more AD you get him, so the bonus damage for leveling it isn't really that great.

- This lovely skill grants you an increase and damage and also more lifesteal and vamp. This is great in 1v1's. Using this item with other lifesteal items double your healing, making you pretty much OP in 1v1. 30-40 lifesteal between start and mid game, 100+ lifesteal at end game.

- Gives you the power to hit enemies with true damage, but inflicting damage on yourself. This is the best thing about Olaf. Basically, armor doesn't apply to this move, meaning your gonna get the damage you want. 340 True Damage can whack 25-40 percent of their health, depending if they're just tanky or squish it doesn't matter, because it's true damage. Always use this when you can.

- THIS ultimate, great escape and a great initiation. Reduces incoming damage and stops all disables. NOT to mention the armor pen passive. Getting exhausted, stunned, snared, it doesn't matter after you pop this ult.

Core Build

- This is a great start item, because it mixes with your Vicious Strikes, meaning if you're low health, you can lifesteal a good 40-50 with your added Vicious Strikes.

- I just get him this mainly because it adds a bit more attack speed, you can also go for a Mercury Treads but you've got an ultimate for a reason. Either way it's up to you.

- Your chosen item. Always get this, no matter what. It provides a tonne of hp which helps a lot. With the self inflict of your Reckless Swing, it's a really good item because you get a bit of damage and helps you survive and go for a kill.

- I get this mainly for the Armor Pen and Attack Speed/Damage. Olaf will be hitting really hard with both the passive and Vicious Strikes. Your going to be doing a good deal of damage also to them tanks which makes you really powerful in 1v1 situations.

- Banshee's Veil is a little something to perk up your magic resist and health/mana. It's got a great passive and it may become useful against CC characters.

- You should turn your Vampiric Scepter into one of these babies, as it gives you up to 100 damage and 25% lifesteal. Added with your Vicious Strikes, thats 46% lifesteal. You'll be able to lifesteal 100+ health right there.

6th Item

- Perks up your armor, and gives you damage of 2% of your max health. That's at least a 50+, so it's a great last item to your build.

- This gives you some more attack speed, critical chance and also some movement speed. That a lot more chasing and damage for you. Another great item.

These are the 2 Spells I mostly use when playing Olaf. Exhaust providing great chase or to slow while escaping, Ghost also used to escape or chase along with your ultimate.

Another Great Summoner Spell

- Use your ultimate, go through a wall. Great escape items or just to get a little closer in range. Flash is an item that will save your life. Your Guardian Angel. x]

I pick up undertow at level 1, then go for both reckless swing and vicious strikes. Try to max out reckless swing first, vicious strikes second and pick up your ult when you can.

This is still under maintenance. I'll be adding whatever so be sure to tell me what you want in this build. Some opinions would be nice. I'm no Professional gamer but I do hope you find this guide a bit of help.

THANK YOU .