Because there are a lot of helicopter haters out there, this is how you do it properly:
Stand sideways on to the target with your throwing arm extended directly away from the target, elbow bent to raise the hand.
Hold the loaded pouch with your other hand towards the target so the cords pass over your head.
With the pouch hand, pull the pouch sideways and release it into a horizontal spin. Use a twirl of the throwing arm to put more energy into the spin.
The pouch now spins horizontally above your head. Use only your wrist to maintain the spin, dont use your whole arm. Its like stirring a cup of coffee, not stirring a pot of stew. Relax your arm, rotate your wrist.
Make sure the center of the circle is behind you. A common beginner error is to try and make your head the centre of the circle. This makes the throw very weak. Get your elbow back behind you and spin with the wrist.
Dont try to put lots of energy into the spin. Another common beginner error is to try and spin as fast as possible. Use only enough spin to keep the pouch horizontal. Any more than that is a waste.
Start a count of the spins as they cross in front of you. The count is 'One.... two.... THROW!'
When you throw, stop rotating your wrist and drive your hand straight towards the target. It is vital that the throw is straight. It is not a bigger spin, or a faster spin, or any kind of spin at all. You are throwing the center of the circle from as far back as possible straight towards the target.
During the throw you will feel a surge of centrifugal force as the pouch whips around behind your hand. It pulls back against your throw. When this surge dies away, let go of the release cord.
As the open sling whips around in front of you, use your free hand to grab the retention cord a short distance from your throwing hand. Pull the sling through your free hand until you reach the pouch.
With your throwing hand, take your next ammo. Bring the ammo to the open pouch. Use your pouch hand to fold the pouch around the ammo and hold it.
With your throwing hand take the dangling release cord and slide it through your grip until you reach the knot. You are now ready to throw again.
http://www.youtube.com/watch?v=4GXkmT7eJFo