Lee Sin has been one of the most popular and strongest junglers in both solo queue and competitive play for a while now. He has a lot of tools at his disposal but he takes a while to master. Lee Sin is really strong early game which he can use to pressure lanes or the enemy jungler. From there, Lee Sin scales into the mid game by taking vision control of the map with his mobility and Sightstone, then transitions into a utility based tank late game.

I use 21/9/0 masteries for Lee Sin which accents his early game strength by giving him more damage from offense and a bit more survivability from defense.

I use Greater Mark of Attack Damage, Greater Seal of Armor, Greater Glyph of Magic Resist, and Greater Quintessence of Attack Damage which is a standard page for any AD jungler. Anything close to this is fine as well; Greater Mark of Armor Penetration is fine and so are Greater Glyph of Scaling Magic Resist and Greater Glyph of Cooldown Reduction. I prefer CDR glyphs when the other team doesn't have much magic damage or when my mid laner doesn't need blue.

(Passive) Flurry
Lee Sin's passive gives him bonus attack speed for two auto attacks after you cast a spell. Each autoattack restores energy as well. This makes it ideal to space one or two autoattacks in between your abilities when jungling or fighting to keep up your energy and make use of the attack speed.

(Q) Sonic Wave / Resonating Strike
Cooldown: 11/10/9/8/7 seconds
Lee Sin's Q is a skill-shot nuke that deals damage, reveals, and allows him to cast it again to dash to the enemy and deal more damage based on how much health they're missing.

This is Lee Sin's core ability in the early game, being able to hit your Q is everything. I've found that being patient with the Q is the best way to hit it. If you shoot it at max range it's easy for people to dodge, but if you run at your enemies they'll usually waste time juking and allow you to catch up to them due to Lee Sin's high base movement speed, or they'll run away in a straight line which makes them easy to hit.

There is a huge urge to want to follow up on any Q that you hit but be careful because it's not worth it if it gets you killed.

(W) Safeguard / Iron Will
Cooldown: 9 seconds
Lee Sin's W is a dash that he can use on himself or allies that gives a small shield for 2 seconds, it gets a reduced cool-down if it's used on a champion (including himself). If he activates W again, he gains a lot of life steal and spell vamp for 4 seconds.

There are a few tricks with Lee Sin's W that can make it more effective. I'd recommend that everyone who plays Lee Sin to make a separate hotkey to self cast this ability, because it's a lot easier than moving your mouse to target yourself every time you want to use it while clearing the jungle.

Another way to make use of this ability is by using it to jump to wards. Ward jumping is a huge part about playing Lee Sin. To make it easier, make sure you smart cast wards and this spell so that you can do it really fast. I set my smartcast item slot 2 hotkey to C, so when I want to ward jump I press C then W at the same point which makes the ward jump really fluent.

You can also use your W to cancel the 2nd part of your Q. You can use this to dash at an enemy to make them think you're going on them then jump away before the ability connects. It won't do any damage but it can get in your opponents head or make them waste spells thinking that you're initiating. Just be careful because the dash from your Q goes really fast and if you press W too slow you'll go all the way in.

(W) Tempest / Cripple
Cooldown: 10 seconds
Lee Sin's E is an AoE magic damage nuke that also reveals units that he hits. Activating it again will slow everyone's movement speed that got hit by the initial E.

This ability is a bit underwhelming after the 4.13 nerfs because it doesn't slow attack speed any more but it's still a nice AoE slow and nuke.

The only trick with this ability is that you can E then Flash and it makes your E apply to the area that you Flashed to. You won't use this trick every game but sometimes you can catch people off guard with it because it's faster than using Flash then E.

(R) Dragon's Rage
Cooldown: 90/75/60 seconds
Lee Sin's ult is a high damage nuke that knocks his target backwards and knocks up any enemy that the target gets knocked into.

Lee Sin's ult can be used a ton of different ways which makes incredibly versatile. You can initiate a fight by getting behind someone and kicking them into your team, you can kick someone through the rest of their team to knock up all of them, you can use the kick to peel for your carries, or you can use it to "secure" kills for yourself.

You can also ult then Flash just like you can with the E. It's pretty hard to do and it runs the risk of wasting your ult and Flash to save an enemy, but if you pull it off it's almost impossible to react to and looks really cool.