The runes are made so that you will have a ton of armor pen, i know that many say its not neccesary because of the passive from his ulti, BUT more and more people have realised that armor is important so they are getting more and more making it harder to be meele DPS/carry if you dont follow the flow and get some pen, the seal is armor.... you might be like WTF ARMOR ARE YOU STUPID? .... but no, im not the armor is so imåportant because as said just some seconds ago more and more get armor to protect from DPS and so should you no matter what char youre playing, besides thers so good runes to take in seals anyway besides like regen and dodge, but you wont need the dodge and the regen is out og the question because of the lifesteal, and yes even in low lvl the lifesteal will 90% of the time be alot better.

The items ....
the build order is a litle wierd you might think .. but try it out :) it works very fell because of the massive lifesteal.. the phantom dancer is mostly for AS although you get AS from your passive it dosnt give you at full health wich makes you intiation poor, here from you can mix as you want, i normaly take IE if my money allows it then BT then warmog and atmas, the reason for this is that both atmas give dmg and your W does from the health from warmog, althoug some would take atmas first because of money, dmg and armor i do warmogs first because if the game is this long it wont take you long to farm up for at atmas and at that point your bonus hp from warmogs is up too making it more potent and have bertter synergy with your skills and dmg output, if the game aint so long or maybe you aint so good at last hitting then i recomend starks for the spped and lifesteal althoug its not as powerfull as BT (obviosly) then a Last whisper for more dmg and some pen against thoose tricky tanks and a frozen mallet for some hp and dmg wich lso goes well with your W.
you can mix as you want with all the items most build orders tend to work out although this is the one i find my self playing best with.

The skill sequence is a mix between vicious and reckless, this is because the life and spell vamp from vicious is extremly good for healing up, dmg output and staying alive during combat, you can take whatever you fell for most it all works out and often depends on the enemies your playing against, like if you play against high phys armor do reckless since it goes through all armor if meele but not tanky do vicious so you can kill and take a beating at the same time, if ranged carries i would go for reckless since they can out manouver you and do dmg before you get there and reckless is a more solid dmg input and has a range for thoose who are lucky enough to get the chance to get away, ranged AP again vicious so that you can sray alive and get after a burst, youre most likely to survive the first couple of sec of the AP dmg and then its just important that you get there (using ulti so you wont get stun, ensnare etc. etc.) and get in some punches to keep you alive and then after they got the CD up its just a piece of cakes chopping them up. The reason for me only taking 1 point in undertow is that you get the slow, you get the dmg, and yes i also know that you cant throw in undertow to take some with low hp out becuase the dmg is low but thats when you ghost in use reckless and run like hell no problem just as easy as undertow exept you'll be more dangerous in toe to toe combat.

Exhaust: well do i even need to say anything? its the best tool for any champ in the whole game almost... its so extremly good lowers dmg no matter what you are and what you build, and the slow is really good for thoes tight situations or shutting down that overfeeded meelee.

Ghost: i pick ghost as my second skill because its the greatest tool of all time, i simply love this skill, its so good because of the speed bonus you'le be able to catch any1 espeially if you know how to use your undertow, and i know flash is better for suprises and wall jumping, but its just not worth it cause its so easy to get away if the have ghost and you have flash, yes you get close but 0.2 sec later they are out of range so its just a complete ****ing waste.

When playing ranked you have to be very carefull when focusing, take down the DPS first since unless you got convinces something else taking the CC wont benecesary because of your ulti so unless its a big team fight and youre the only real dmg output you shouldnt be going for the CC, but if youre the only like real dmg on the team so far you should go for the CC to help your team dont be a **** head, after all it is a team game :)

Enemies that you should handle with extra care: morde because os his shield and his ulti being a big burst if youre low on life it cant take you out alone or with a mace of spades

Annie: well because she has the most extreme burst dmg in the game and can take out almost any non 90% mag res tank in 1 burst.

Cho: be carefull about attacking cho at low health because of his ulti doing up to a minimum of 650 true dmg wich is really alot if youre trying with like 100 to heal up before he gets in his ulti.

poppy: because she has some really epic dmg but mostly because of her passive making her extremly tough the last 20% of her health to take down.

rammus: usally a problem early game since although he has defensive ball and prob thorn you most likely can out heal him when he gets out of defensive so if youre not taunted try not to attack when he is in defensive mode else you prob kill yourself.

vlad: vlad is also a ***** fighting but this is with all meele because of his much nerf needed aguine pool wich well to say the least is ****ing op...

Remember to be offensive, i know its a litle wierd but olaf is prob the best meele champ in the game so why not use that and pwn some unexpecting noobs, final advice is dont be afraid take some chances, standing in the push with 12 hp? been there 12 hp and yi coming with ulti on i pop my ulti, vicious and reckless and start clobbering him, i start out with a crit healing me almost 200 hp and therefrom hes just getting beaten even though he has ulti and more dmg than me the vamp is so heavy that i take him down with 800 hp left... wait what? 800? yeah thats right gained 788 hp on fighting so dont be afraid take a risk after all if you **** up.. its just a game :)