This guide is for a level one invade as lee sin mid.
At level one, lee sin has INSANE kill potential. This is a very high risk/high reward cheese move that can make or break you early. On blue side head to the enemy jungle on the top lane side. Go to the brush behind red. Wait patiently, and hope for the best.
On Red side, do the same, but go to bot jungle behind their red buff.
NOTE: If the person you encounter has heal or barrier, then don't try this.