Step 1: Type of Pencil
For reasons explained later, it's better if the pencil is sharp. However, watch out for eyeballs when throwing sharp pencils!
Step 2: Holding the Pencil
Place the tip of the pencil in between these digits, such that when you do click your fingers you will be rolling the pencil.
Step 3: Launching
The pencil will leave your hand with such spin that it will hum.