Learning to throw knives is no easy task but it's certainly not impossible. Knife throwing is more about finesse than power. Too many people make the mistake of throwing a knife as hard as they can, but too much force in your throw causes the knife to ricochet instead of sticking. The two most important aspects of knife throwing are proper grip and a free and natural release.
While there are many ways that you can hold a throwing knife the two most popular holds are the hammer grip and the pinch grip. The hammer grip is aptly named because the hold closely resembles the way a person would hold a hammer. With the hammer grip, the edge of the knife should be held between the thumb and index finger, with the thumb resting on the spine of the blade or handle. For a successful throw from this position the wrist must remain still but relaxed upon release. The arm dropping and the knife leaving the hand should be carried out in one continuous and fluid motion. The hammer grip is best suited for heavier knives with longer blades.
The pinch grip is used to throw smaller blades with force. Using the pinch grip the knife is placed between the thumb and forefinger at its center or fulcrum where the weight is evenly balanced. This should always be done with an unsharpened blade. The knife should extend out straight as an extension of the arm. Hold the knife firmly while retaining a relaxed grip. A grip that is too loose or to tight will result in a loss of accuracy.
When throwing keep the foot opposite your throwing arm one step behind the foot of your non- throwing arm. The distance between your feet should be approximately two shoe lengths. Raise your throwing arm above your head as if you were intending to cut or chop something in front of and above you. As your raise your arm, your weight should rest on the ball of the foot that is on the same side of your throwing arm. As you drop your arm to line up with your target, you will shift the weight from the side of your throwing arm to your front foot. Release the knife when it is even with your target, but don't stop your throwing motion. The follow through is very import to ensure the knife sticks. The motion of throwing a knife is very similar to throwing a baseball except that the thumb is released instead of the index finger. There are several books available like Knife Throwing: A Practical Guide by Henry K. McEvoy to help you perfect your technique.