Do tell, about this method...
I don't understand about the rotating 1/2 of a turn or 1/4 of a turn. Like I said I know nothing about throwing. Can someone explain this to me?
Oh, boy, the limits of textual medium! Let me try.
Okay, 1/2 turns, full turns etc, to start. When you throw from short range, say, you begin to practice by throwing a knife into the ground in front of your feet, you'll find that you have to grip the knife by the blade. (How exactly you hold it depends on your style, and whether it's a dagger.) When you throw it, the knife will leave your hand with the handle pointing toward the target, rotate 1/2 of a turn, and will strike the target with the tip.
If you move back (typically about 3 feet) you'll have to hold the handle to hit the target. The knife will make one full turn (point-handle-point) and strike the target. Move back another 3 feet, and you switch to the blade again for a 1 1/2 turn throw. Continue until you can't achieve consistency with your rotations, and the knife hits at random points through the rotation. (Usually what happens in the movies, except they always magically land in the correct position.) This is why knife-throwing is more of a sport than an actual self-defense. You have to learn to throw from certain distances. In between those distances is very hard to learn consistently. (3' and 6' is easy - 5' is extremely difficult.)
Now, for the 1/4 turn, or "direct hit" method. We get technical.
For any throw, whether it be a baseball, knife, rock, whatever, we don't release the object when it is in front of us - or we would throw it directly into our feet. We release when we are at the very top of the rotation of the throw. (Think of throwing a football.) That way the force goes forward, toward your target.
So, technically, whenever we release a knife for throwing, it actually spins an extra 1/4 of a turn while in the air. A 1/2 turn throw actually leaves your hand with the handle pointing straight up in the air, and rotates 3/4 of a turn before it strikes.
With this in mind, we've bought ourselves a extra 1/4 of a turn to fit the throw. We need this, because the momentum of the throw itself gives a turning motion to the knife. So, now we eliminate the extra spins!
To do this: balance the spike (it's easier if the spike is balanced at the center, but not necessary) at the end of two fingers, with the handle resting in your palm. It's recommended that you use the two middle fingers, but I prefer the first two fingers, like throwing a baseball. Finding the point of balance is critical - eventually you'll find it instinctively.
To throw, you're trying to push the center of balance (COB) of the spike towards the target. The natural rotation imparted by the throw will cause the spike to continue to rotate slowly. This is good for about 10 feet. The spike will leave your hand with the point straight up and down, and will slowly drop to face the target. There you go - direct hit!
Each person will have a different "beginning point" for the "natural" part of the throw - that is, a throw from the COB. Move forward and back until you find yours. (Throw from here about 1,000 times.)
Now, to adjust for distance. If you want to move back, slide your fingers until the spike (aka bo-shiruken) is slightly point-heavy. This will counteract the natural rotation of the throw, and will cause the spike to rotate more slowly. If you go too far, the spike won't rotate at all, but will "float" towards the target with the point straight up and down.
Since 1/4 turn spread out over 20 feet is pretty slow, its not much different than 30 feet, or 40 feet. So, the farther you get away, the less accurate of a judge of distance you have to be! Also, the arc of the throw begins to correlate to the amount of spin, so that the point stays at the lead.
If you want to move closer than 10 feet, balance the spike so that it is handle-heavy. This will push the blade a little more, and cause the spike to rotate faster. In this way you can be touching the target with one hand, and sticking it with the other. I find that my most difficult distance is about 4 feet. (Harder than 40, actually.) It's here that I sometime switch to a 1/2 turn (actually a 3/4 turn) throw.
After a while, you will learn the proper balance for certain distances.
Questions?
I would post a video, but it wouldn't help!