This is my first guide how to jungle with Lee sin, so please rate and comment! :)
Lee sin is a quite hard champion to learn, but when you play him a lot you will get used to him and he will be very fun to play :)

First i go with Tempest/Cripple beacuse of the AoE and the Slow & Attack speed debuff. Then i go with Safeguard/Iron Will and on lv 3 i go with sonic wave/reasonating strike.
When i got 1 point in all skills i max out Sonic wave/reasonating strike. Beacuse its the best spell for ganking, and it does huge early game damage. Its also good for jungeling. For example when you are going to kill Lizard, you do some damage and the use Sonic wave and the smite, and then Reasonating strike (Beacuse the less HP the minon has the more damage output do do).
Then you put in Dragons Rage at Lv 6, and max out Sonic Wave/Reasonating strike, and then switch between Safeguard/Ironwill and Tempest/Cripple. If your facing a huge DPS team, you max out Tempest/Cripple beacuse it slows and reduces the attack speed. If your facing a huge Caster team with a lot of AP, you max out Safeguard/Iron will because it works so good with hexdrinker.

I start with Vampiric scepter, build Wriggle's Lantern when you got enough gold. Then i build Mercenary treads. After you got your core early game items, you build Hexdrinker, because it procs with Safeguard/Iron will, will block a lot of damage early on. These are your core items early/mid game. If your facing a lot of DPS champions on the oppsiting teams, get sunfire cape. Good aura damage, health and armror. If your facing a lot of AP casters, Buy a negatron cloack and then build the Sunfire cape. These itemes is really important to have around early game for survivablity and damage output. You can either build a Banshee's Viel or Force of Nature, your choice. I always go with Banshee's viel, because it also blocks one spell. And at last there are some options what you can buy. Either Atma's Impaler, Wit's end, or Hextech Revolver, its up to you what you need.

There is some different routes that you can use but i reccomend this one.
1. Start with gathering your teammates at blue, let mid and let your teammates defend it, when blue spawns, will mid player use one spell to pull and you use Tempest. attack two times (Passive) and then use Cripple. Let your teammates which are helping you defending do some damage and then you can handel it buy your own with smite. Then go to wolves and kill them, if you have enough of HP and think you can handle wraiths do that too, but i recommend to Recall.
2.Buy Cloth armor and 1-2 Health pots, go with wraiths (if you didn't kill them before you recalled), then golems. Recall and buy your boots.
3.Kill red and start ganking. Do this over and over again, go to the other spawns if they dont have another jungler of course.

I always use Flash and of course smite. You can experiment with this this like for example taking ghost instead. But i always use flash for ganking and escaping.

For runes i take standard jungeling seals or resiliance,i go with armor penetration runes and marks and for glyphs i take flat magic resist for early game/mid game survivability.