The rate of spin of the boomerang is much more important to a good flight than a hard toss. To create lots of spin think of the action as an exaggerated knock on a door, or cracking a whip. The uninitiated thrower always thinks it's a sidearm toss, but because of the physics principles we just discussed, a boomerangs flight is perpendicular to the plane of the boomerang so it must be an overhand throw to produce the round returning flight. A sidearm throw will produce a straight up flight with a crashing return, usually resulting in a broken boomerang. The throw produces the thrust.
Wings produce lift.
The spinning produces gyroscopic stability. The lift and the spinning create gyroscopic precession that turns it until it is gently hovering in. So next time you are throwing boomerangs and making momentary sculptures in the sky, consider the science involved, and envision Stone Age man working through technology that wouldn't be fully understood for thousands of years. Information Airfoils - The Basics .