Before you start, remember that knife throwing might feel awkward at first, but at one time so did playing a musical instrument, riding a bike or throwing a football. Any new activity requires time for your body to develop muscle memory and to gain strength. Be patient, and quit when you feel yourself getting tired or sense that your concentration is slipping.
The two most widely used throws are based on a half spin and a full spin of the knife, depending on whether you use a blade grip or handle grip, respectively. As you might imagine, a knife gripped by the blade must complete half a spin before it points in the right direction, whereas a handle-gripped knife begins its flight pointed the right way and must make a full spin to return to it. Although the total number of spins depends on throwing distance, these two styles will always involve some multiple of half or full spins.
Whether throwing by blade or by handle, the technique is the same. First, stand at the appropriate distance (more on that in a minute). Now, balance yourself by standing with the leg opposite your throwing arm forward. Present the knife to the target, sight with it and smoothly bring it back behind your shoulder. Keeping your eye on the target, swing the knife in an arcing, vertical overhand motion and release it near the top of the arc or just after (it will take practice to develop the feel of this). The knife should slip easily out of your hand. Do not whip your wrist. Follow through until your arm extends in front of you as if you were shaking someone's hand. It's common to transfer your weight from the back foot to the front during the throw.
Beyond these basics, you'll need to make adjustments based on distance, type of knife, stance, body proportions and throwing style. For a half-turn throw (blade grip), you'll usually throw from around 7 to 8 feet (2.1 to 2.4 meters). A full-spin throw (handle grip) will require 12 to 15 feet (3.7 to 4.6 meters) to complete one turn, and 18 to 19 feet (5.5 to 5.8 meters) for the more difficult two-spin throw [sources: AKTA; McEvoy].
As with most aspects of knife throwing, distance requires some dialing in. If your knife enters the target with the handle slanting toward the ground, then you are standing a bit too close. Try moving another 6 inches (15 centimeters) back from the target. If the handle is angled upward, then you are standing too far away [sources: AKTA; AKTA]. Once you have your distance, the rest is a question of grip and technique.