The key to throwing a knife or axe is consistency. Let your body and the knife work together for a comfortable and consistent performance. Distance and accuracy is unimportant at first, it is more important to get successful sticks.
The relationship between body size and the tool you are throwing will dictate the distance you should throw the tool from. Generally speaking, smaller length tools require shorter distances. Each different tool will require a different distance (it may be a small change but a difference none the less).
Try the following to establish your comfortable and successful distance:
1. stand with back to target
2. take 5 normal steps away from the target
3. place a mark at your toe and face the target
4. begin throwing and observing from this initial distance
5. adjust the distance, and mark it
6. when you find a distance that produces a consistent stick rate, 75%, record that distance (in feet or steps) for that tool. It should change very little from day to day.
The above is based on consistency. If you are trying new techniques, tired or otherwise not using your consistent delivery, things will not go so well.
For competitive issues, the only thing that should change is your knife/hawk and your distance. The way you throw should be consistent.
After you get the one-turn above down, just add 3 more steps to get 2 turns, 6 more for 3 turns etc. Half turns will be somewhere inbetween, just experiment.