so this is a brief introduction since my first one was erased (grrr). pretty much three things. this will teach you my mediocre builds, nothing too advanced, but should get you through most games. I'll show you some basic Jungle Routes, and a few mid-league tips about playing olaf. If you want super advanced go somewhere else. if olaf is played correctly, you and you're tank will suicide run in there, kill their carry, and perhaps survived. too late or too early initiated will end up with the death of everyone on your team. sucks for you. also, check out my AP morde build if you'd like. I would love feedback and please try out the build and sctuff before voting. thanks.

Go Blue>wolves>wraiths>small golems>red> or Blue>...>...>re>small golems> or don't do red and just gank. olaf doesn't need red to gank but it helps. you can do safe warwick route but you are too low to gank. the route is small golems>wraiths>wolves>blue>red>
Alternate Route

Marks:
Armor Pen(best on olaf, Add to his ridiculous armor pen
AD (I think they suck but preference I guess)
AS (It doesn't really help much)
Seals:
Armor (help you jungle and make your health way more effective
Dodge (against DPS you ignore 6% damage)
Mana Regen (you're jungling. you don't need that)
Health: **** **** ****. it's like 45 health. health Per level surpasses that at level 5.
Glyphs:
Magic Resist: per level and flat are pretty good but per level is better
CDR per level: would not recommend getting flat CDR since it is surpassed by per level at 12 or 13. not as good as M rez but they'll get the job done.
Quints
ArP: extremely good 10 more ArP is awesome
Flat Health: these are viable although I don't like them as much anymore since the nerf. still pretty good though.
you should not get any other quints for him
note: I understand if you cannot afford runes and stuff and are using like warwick runes. that fine. but I don't want is like I'm going to buy 9 AS marks for Olaf. they are sooo good. that's stupid.

Olaf doesn't have the greatest lane ability as his harass is very long CD and mana-hungry. he can lane fine not great, and if you don't feel straight up to jungling right now that's fine. But I urge you to learn or practice it if you want to continue playing olaf.

I used to personally lean to Mercury's treads in solo queue because I could never get a great team to olaf's playstyle. I would recommend Mercs if your team rarely commits to team fights, like a team that just kites back, kills a few, and then pushes, I would recommend merc treads. If both teams are like that you probably should get mercs. this is because you cannot have your ultimate on all the time in every little skirmish. It really helps with teams like that.

On the other hand, If you are with a arranged team on vent/similar thing really try to coordinate a team comp that suits olaf's "run in there" strategy. a good team for this would be Olaf, Kennen, Jarvan, Ashe, Taric. Jarvan runs in there, popping them all up and trapping them, kennen follows with his ult, Ashe stuns someone, you run in there, Taric is just a magical heal bus, and then Ashe cleans up. with a team like this it's usually a one team fight thing. I would get Zerker Greaves with this team.

These are items you must, must, must get on olaf. they are extremely good on him and make him what he is
Frozen Mallet : This was made for olaf. this is the equivalent to Infinity edge on ashe, Madreds Bloodrazors on warwick, and sunfire cape on garen. this gives you health for your passive (more health means that you can get the same amount of attack speed from your missing health with more health left over. Ex. if you have 2000 health missing 200 health gets you 10% attack speed with 1800 health. 3000 health missing 1200 health gets you 40% attack speed with 1800 health) and the health also gives you more AD from your W ability (1% of 700 is 7 AD), 20 AD, and a slow. so in total, you get
Frozen mallet:
700 health
20-41(w. Atmas) AD
a 35% constant slow
plus an increase percentage in AS
honestly, besides the early wriggle for jungling you don't really have any set build besides
Wriggles, Merc Treads and Frozen mallet.

here's where you can mix it up a bit. two items i think are really awesome on olaf are ghostblade and atma's impaler. Ghostblade is a great item because it gives you so many good stats for olaf such as:
Yoummuu's Ghostblade:

20 armor pen (this adds to you already ridiculous armor pen which gets to with just runes and masteries you get 31 armor pen plus 30 with your passive so you get a grand total of 81 armor pen.
30 AD (a decent amount of AD)
15% crit chance (decent amount)
20% CDR (a B-E-A-UTIFUL amount of cooldown)
epic active

the active gives you AS and movement speed for up to 14 seconds in combination with you ult makes you a truck of pain.
Atma's Impaler:

45 armor
18% crit chance
passive: 2% of your max health is converted into AD (pretty much doubles your W ability)

This is great on olaf. the extra armor gives him survivability, the Crit Chance is awesome, and the passive is rape on him. plus you're w, this gives you 3% of your max health in AD. if you have 3000 health, that's 90 AD. that's two Bf swords, at the same cost, but this gives you armor AND crit chance.
warmog's armor:

920 flat health (pretty rape on olaf if you ask me)
30 health regen per 5 (not the greatest on him, but decent between fights)
passive: gain up to 450 bonus health and 15 bonus health regen per 5

no explanations really needed. this gives you a grand total of 1370 health, translating to 41 AD from this alone(with atmas). really risky if they have madred's bloodrazors or a deathfires grasp because it will destroy you. also just a tip in general do not stack health if they have a Madreds or a deathfires grasp OR a madred's typeish ability(ex kog maw's w ability or vaynes w). just get resistances with a bit of health instead. I know, it sucks. you mean I can't get 3 warmogs? sorry timmy, you'll just have to stick to 3k health.
Force of Nature:

76 magic resist
8% movement speed
40 health regen per 5
passive: regen .35% of your max health every second

many people like banshee veil on olaf, and thats fine. but if you're going against castors that deal lots of Magic damage over time, like kiters (I.E. Cassiopeia or teemo or malzahar.) then this is much better. the movement speed makes you rape, allowing you to be up there with your ult on for longer, the magic resist is a **** ton, and the regen is ridiculous on olaf. you get a flat 40, plus .0035*3000*5= 52.5 more health regen, bringing it too a 92.5 regen per 5 at level 18. this, plus you're lifesteal, will keep you alive longer at lower health.
Starks Fervor:

20% attack speed
Aura: 30% attack speed, 20% lifesteal, and 30 health regen per 5

the attack speed is awesome, the lifesteal is ridiculous (you're leveled up w plus the wriggles plus this gives you 51% lifesteal) the regen is nice and the aura is pretty good. you can get this even if someone on your team already has it since it stacks on the aura holders up to twice, but not more than that. pretty nice item on olaf if you need a bit more AS and lifesteal. also the negative Debuff is kind of like 30 armor pen, which adds to your insane amount already. hey, the more the merrier, am I right?
black Cleaver:

55 Attack Damage
30% Attack Speed
Passive: Physical attacks reduce your target's Armor by 15 for 5 seconds (maximum 3 stacks).

the passive acts as a theoretical 45 armor pen. adding to your 61 armor pen (runes, masteries, passive) this gets you 106 armor pen. that negates a glacial shroud with 7 armor pen to spare.
Last whisper:

40 AD
40% Armor Pen

I just love, love, LOVE armor pen on olaf. It's pretty much his thing. the way Armor pen scales now is flat then percentage, making this much better at low-mid armor levels but not too OP against High Armor levels. Let's say that amumu has 300 armor. that's a decent amount. but let's say you got Last Whisper and black cleaver. 300-61(Runes, Masteries, Passive)-45(Black Cleaver) *.4(Last Whisper)=77.6(rounded 77) armor. that means you just negated 5000 gold worth in armor. pretty good if you ask me.

hexdrinker:

35 AD
34 MR
passive: when you health drops below 30% of your max health, you gain a shield of 300 health that absorbs ONLY magic damage

if burst castors are f**king you over than this is a good item to get. the 300 damage shield gives you a bit of magic health to have in your defense.
Guardian's angel:

74 armor
34 magic resist
passive: upon death you revive with 750 health and 325 mana

the armor's nice, the MR is nice and the passive is good. nice item to get.

I won't go into detail to much in this section, otherwise it wouldn't end. I'll say just the general idea behind these items
Frozen Heart/ Randuin's Omen
these are taken if they have a lot of high attack speed champions
Infinity Edge
Crit chance, Damage, plus extra crit chance. decent item.
Bloodthirster
Lotsa Damage, Lifesteal. Requires farm.
Sunfire Cape
some armor, some health, aoe magic damage. okay item
Shurelyia's Reverie
only get this if you are against a ridiculous movement speed team. other than that pretty bad item.
Madred's Bloodrazors
alright before you get this or call me noob for getting this let me explain why this is an option. you're passive gives you attack speed, and you're w gives you the spell vamp from the magic damage, so this IS an option-able item against a heavy health team. I wouldn't recommend this in most games. other than that, pretty bad item
Wit's End
since it was revamped, it's a pretty decent item. the extra MR helps, the attack speed is decent, and the on hit effect really does add up. ok item.

any AP item for obvious reasons
Trinity force
I see where it could work but IDK it doesnt seem to work that well on olaf as it does on other champs
Tiamat
cuz its ffin tiamat
Manamune
WHY WOULD you even get this
nahsor's tooth
don't go to me and say, but it gives CD and AS. yea, so does GHOSTBLADE. but guess what? that's actually useful
spirit visage
better to get lifesteal and since the nerf not really worth it
soul shroud
you really shouldn't need the mana regen
Hextech Gunblade
expensive as ****, you don't need the lifesteal OR spellvamp and you don't need the active. 3 things: Q, Frozen mallet and red. nuff said
Phantom Dancer
why do you, Olaf, need straight up attack speed when your passive gives you it?
Cloak and Dagger
you're probably like, this gives tenacity so i can get zerker greaves instead, YAAAAY! NO. just no. I would rather you get Merc Treads and phantom dancer than that. more tenacity, other items give AS. that is all.
Chalice of Harmony
you don't need the mana regen. you SHOUlD be jungling, and if you aren't then I don't know why you aren't.

in team fights, GO FOR THEIR CARRY. you want to pop all the movement speed you got and chase down that ashe with your alistar as you watch malzahar ineffectively try to ult you. Olaf is all about the balance of health and lifesteal, AS. getting too low will end up with you dead. If you realize that you can't lifesteal tank get out. if you can't get out, KEEP HITTING THAT SUCKER. you might kill him or your team will. you are poky IF you have the mana to be. if you have blue abuse it. spam your axe before battles.

expect to be ganked at blue and prepare. perhaps start somewhere else if its too much and your team isn't strong level 1. your axe is pretty good in level 1 team fights, but your jungle time is severely affected. work with your team for ganks and that's pretty much it