When in lane phase you will want to poke your target down with your q, and when they are on about half health go in with your q, then auto attack for your passive and then e, auto attack, e again, and auto attack and finally w, then auto attack and w again. If you are level six ult then q them to get back into them.

When farming you will want to mainly auto attack and e if you like, keep your w for escaping and only use it if you need to life steal back up, keep your q for poking them and going in if you want to kill them.

When in team fights as your going carry lee sin, you will want to q targets until you see someone low and go in and try to kill everyone to maximize your damage try to e as many targets around you for the full area effect damage.

If you need to escape team fights remember to keep a ward on you or someone near so you can w to them for the escape.

When diving make sure you have minions/wards with you so you can w away. When diving in you will want to q, e then ult to kill them ( if you are diving make sure they are low) and then w out.

Pros:

-Mobility
-Burst
-Easy farm
-Sustain
Cons:

-late game not very good
-Squishy early game
-Little health with this build
-CC will get him killed