Hi there,
Since mobafire isnt up to date with the new runes, I will type my runes in the next chapter.
Lee Sin is the most versityle, fun and simply the best champ in game. The main reason for me writing this is that I find most guides on Lee totally wrong!

This is a jungle only guide since i find thats were Lee belongs.
It seems that most ppl think that Lee is a tank! this is wrong!
He is a great ganker, great last hitter and most of all a great assasin. Not that Lee shouldnt be tanky. See my build and u will see.

As mentioned in the intro i will type my rune build.

I find the new runes great!

Full lifesteal quintesses, sometimes i use 1 MS Quint

Full armor pen or ad Marks

Full max health % seals

Full cd glyhps

As mentioned Lee Sin is very versityle and I usually have 3 different rune builds ready for him.
I will explain my rune build in the item and mastery chapter since they are very much combined.

My items are very much combined with my pick of runes, masteries, spells and abilities.

I buy dorans blade as first item!

This is because: Full lifesteal Quint and masteries gives me a 12% lifesteal at lvl 1. Whitch is plenty for jungling atleast when u lvl Safe Guard at lvl 1 gives u an extra 5 % LS. With this item u get the a bit of everything and thats what Lee needs. The 100 HP gives him more than most and the DMG/LS is plenty for the new jungle.

Second item must be boots. Lee needs ms bad for getting his basic attacks in and for chasing moving in jungle.

third item is vampiric scepter or madreds razor, depending on when u shop. Very fast jungling and boosting ur health bar in jungle.

then Lantern, a core item for Lee, saves alot of money on wards whitch is the main consumable needed for Lee. Another all around item. This gives u a big LS.

Phage, The slow is amzing with red buff and the AS boost from passive u can lock down even the fastest champs.

Boots upgrade, multiple choices, dodge boots are still good for heavy AD, Mercury's against CC, swiftness playing against fast champs, mobility boots are great early game! selling them late/mid game for swiftness is usually a very good investment.

Attack speed dagger. a boost for Lee's AS i find important, his jungling improves allot, but more important u hit 20% faster!! Ofc i have AS in masteries and his passive is a great boost. But, early game his cooldowns are longer meaning that the passive isnt as good. And the key to getting kills with Lee is his basic attacks.

Levithian armor or ruby stone and zeal.

Since i have Max HP % increase on my seals, and extra HP in masteries, getting HP is core in this build. If u are doing well and ur team isnt failing their lanes Levithian is a great item. Lee sin often gets last hits, atleast when ganking lanes. And he often gets assist with his AOE abilities. So getting levithian can be a great idea. Giving u lots of HP for a very small amount and the passive is just crazy.
If i chose not to get levithian i upgrade to zeal and buy a ruby stone for a warmogs.

Upgrading to trinity force!! or getting Warmogs.

This is again very much depending on the specific game but clearly warmogs is the defensive option and Trinity is the offensive.
warmogs is just a great item atleast if ur team is lacking in tankness.
I find more and more ppl not using TF!!!
THIS IS A CORE ITEM! besides from being another all around items it has the amazing passive with 150% extra dmg after ability use! Lee sin having a low cooldown and being able to move in and out of figths this is simply needed. It gives u an MS boost not to underestimate, AS, HP,slow and the passive gives u a crazy crit dmg! 870 crit dmg with almost no dmg items at all.

Next upgrade warmogs or get Atmas impaler

Atmas gives allot of dmg and the armor works great.

The game should be finished but other items can be cloak and dagger if u havent got mercurys.
Tenacity is such a big advantage in any game.

My choice of skills is mostly very offensive, which is how i play.

W: safeguard, is very very good, This is my lvl 1,

Q: Sonic wave, one of the best skills in game. Huge dmg and so sneaky. Can be used in many different ways! forexample: use Q-R-Q boosting ur Q dmg and giving great position. Use Q and wait till they use flash/escape ability and use Q again.

E: Tempest, an amazing aoe skill, gives vision of invisible units and is pretty much an aoe exhaust. Which says it all.

R: Dragons Rage

A great ulti, big dmg, does aoe stun ig used correctly. A good last hit ulti but can be risky to use as last hit. great for escaping enemys, u can knock enemies over walls and into death.
In combination witch sonic wave u can do a huge amount of dmg and give urself a great position for taking the kill.

I know my choice of summoner spells is unusual and there is ofc many ways to do it.

Smite isnt as good as it has been, the new jungle is easier.

Eventhough, Smite is a very nice spell. I take red buff at lvl 1. Being able to take buffs fast is great, and using smite in combo with Q is very nice like Q-Smite-Q.

Flash is also a very good spell for Lee but i find that exhaust is such a good spell that i must have it. It makes me able to initiate with Q into a 1vs2 fight where 1 is low, killing both or 1 and escaping.
Furhtermore Lee already has 2 abilities similiar to flash and he can wall jump with wards and friendlies.
And exhaust is just total disable whitch is great for any assasin.

My jungle path is aggresive going for a gank at lvl 2. I start at red buff, getting a pull and maybe a few hits from teammates. I lvl W first for the LS, armor and the ability with the lowest cooldown.

Second i kill golems, i lvl my Q for a gank bot or mid.

Getting FB at lvl 2 is very possible! having red buff and using exhaust is bad ***. By having armor pen marks and masteries, and exhaust giving and extra 10, I get every AD carry down to about 10 armor or less

i try gank, and farm on with wraiths, wolwes, blue for the champ mid.

gank top

Shop

and so on.

Lee Sin is the best champ ever!!

Not much more to say, well there is but i wont bother :)

have fun!