DISCLAIMER: Hey guys! This is my first guide on Mobafire, or anywhere for that matter, so be kind if you will. Keep the criticism constructive, and that's all I ask.

Olaf is one of my favorite champions in the game. He's very strong in lane, or in jungle, has an amazing kit, can stand toe-to-toe with most other champions, and is overall quite a bit of fun to play (in my opinion anyway.) He's a very versatile champion, with the ability to be played in many different ways, but of all the ways I've tried, my favorite by far has been a sort of AD carry type build with a mix bit of 'tankyness' behind him. Endgame your Olaf will have a decent bit of health, armor, and MR, and at the same time, be a wrecking machine with his combination of damage output and attack speed. Autoattacks will be enough to handle most champs, let alone your W and E abilities which up your attack damage and deal true damage respectively, will make Olaf truly deserving of the title Berserker.

Pros:
-High damage throughout the game
-Can stand toe-to-toe with almost any champion
-Ragnarok is one of the best ults in game
-Deals True Damage
-Amazing sustain with life leech
-Can turn the tide of an entire game if played correctly

Cons:
-Prone to kite & harass
-Mana hungry early game
-Somewhat expensive build

Fairly standard runes, Armpen reds and quints, AS seals and MR glyphs (Olaf's MR is lacking compared to his armor unless you go for the more tanky option of this build, but more on that later.)

The Masteries i go with are 21\9\0, and for a fairly simple reason. Olaf is naturally tanky, meaning that as an off tank, you don't have to try very hard to achieve a 'survivable' position in fights. Since we're going for more of an emphasis on damage output than straight up tanking, I choose 21 in offense to give him the boost he needs to keep his damage competitive throughout.

This build starts you off with more of an emphasis on tanking, with a Doran's Shield, which allows you to sustain enough harassment to farm minions in your lane and harass back if you choose to do so. (Olaf's Q is a great harass tool, and E will scare any champ early game) Boots make it easier to chase and the AS, combined with Olaf's passive, make you a force to be reckoned with in lanebased fights (2v2 or 1v1) Wriggle's gives you a nice amount of life leech, combined with your W when needed will allow you to stay in lane for a very long time to soak up XP and last hits.

Your main goal is to collect all this as fast as possible so you can work on Frozen Mallet. Once you get it, provided your team hasn't been feeding, you'll win 9\10 teamfights for your team. After FM, rush Atma's for the armor & a nice damage boost, then grab a cheap Zeal for a pretty decent AS boost. Top it off with a BT and Phantom Dancer whenever you have enough gold to do so (provided you haven't won by this point :P ) and this is where the item guide branches off into a matter of choice.

After the basic build has been completed, you may want to keep it as is (in which case you will do fine) or you might choose to sell Wriggle's and go for another 'late-game' item. What this is depends on what your team, as well as their team, has built so far. If you find yourself dying too easily, pick up a Warmog's (which will provide another nice boost to your health, and consequently, your damage), but if you want to just tear through the other team like a hot knife through snow, either grab another Phantom Dancer or an item that branches off of BF sword (Black Cleaver or Infinity Edge)

This one can be altered to fit your specific playstyle without too much concern, but be certain to pick up at least two points in Reckless Swing early on. Some people say it falls off late game (I disagree considering that it's 340 true damage...nothing to be ignored, period) but it's definitely your biggest powerhouse early on, and will undoubtedly turn fights in your favor if the enemy is ballsy enough to take you on. I like to take Q first because, as previously stated, it's a great tool for harass, and allows you to better chase enemy champs with the slow it provides. E second for the reasons I already stated, and W third to provide you with some early game life steal \ damage boost if necessary. From there, it pretty much depends on your playstyle, so go nuts :P

Viable:
Exhaust - Useful for chasing \ running, disabling AD carries in fights.
Ignite - Good for getting first blood, or against healer-heavy teams (or champs with mucho grande lifesteal\AS i.e Master Yi)
Flash - Best escape summoner spell. Flash away, flash over walls, flash to your turret, or even flash to catch a fleeing enemy.
Ghost - Some prefer this to flash due to the more constant and consistent boost it provides, as well as the ability to not get caught up on minions.
Smite - Only if jungling

Most other spells I don't bother with. Take teleport if you like for more lane control.

Overall, this is my favorite way to play Olaf, and in my personal experience, the way I've found to be most successful. I don't play ranked, so take that into consideration, but as far as my experience goes, this the the most useful & fun way I've found to play Olaf. It may not work for everybody, but at least give it a shot, and good luck!