Learning to throw a knife is strictly trial and error because no two people are built exactly the same. Therefore after one learns the fundamentals as to grasp, stance and follow through, he must develop a style that fits his build.
One should develop the half turn first, however whether the knife is thrown by the blade or handle the grip is the same. When thrown properly a knife makes a half turn every three feet.
The knife should be between 12 and 16 inches long and weigh 15 to 16 ounces and should be formed so that it balances in the middle. Thus it can be thrown by the handle or blade with the same accuracy.
Now for a half turn throw, stand about 8 feet from the target. Keep your eye on the bulls eye and throw overhand and follow through.
To put it in layman's terms, throwing a knife is like throwing a baseball. The pitcher keeps his eye on the spot where he wants the ball to go then follows through after the release.
No matter what the game, be it golf, archery, shooting, etc, one must follow through.
Now at 8 feet the knife lands with the handle in a downward slant you are a little to close. Step back about 6 inches. If the handle is in a upward slant, you must step forward a little.
You must keep this up until the knife lands horizontal every time. Try to throw with the same force so that it will not affect your follow through.
After perfecting the half turn throw you are now ready for the full turn throw. Step back about anywhere from 12 to 15 feet from the target. Hold the knife full by the handle and throw overhand in the same manner as in the half turn throw and remember to follow through as it is the secret in any sport.
Remember practice makes perfect, so practice!