The arm on the left (with hand) is the dingle arm. The arm on the right is the lead arm. Left handed boomerangs would be the opposite.
The bottom of the boomerang (unpainted side) should be against your palm. The top (painted side) should be against your thumb. Remember, spin is more critical than a hard or forceful throw. Your grip should allow the boomerang to begin to spin (rotate) as it leaves your hand. Use what works best for you, and remember spin is king!
Table of Contents
You can continue from here either by using the navigation menu up top labeled "throwing", or by using this table of contents below.