The purpose of the one knee drill is to improve the grip and to increase the quarterback's wrist snap. When throwing from this position, it is not possible to get your whole body into the throw the way you should, therefore, you must emphasize the wrist snap portion of the throwing motion. Remember, slap the wall with the throwing arm.
Kneel on one knee, with the knee down on the side of your throwing arm. The ball should be placed on the ground about one foot in front of the knee that is down. Using only your passing hand, grip the ball and lift it from the ground. Once the ball has cleared the ground, your non-passing hand should also be placed on the ball, so that the two hands together lift it up to a point just above and outside of the quarterback's right ear in a passing position. Make the throw from here by drawing back as you cock your shoulder. Be very careful to avoid the tendency of "winding up" by having to dip the ball way down below the level of the shoulder as you draw it back just prior to throwing.
Try to throw with a straight over-hand motion, emphasizing the snap of the wrist just as the ball is leaving your hand. The palm of your passing hand should roll over completely so that the palm is pointing at a 45 degree angle down and to your outside (slap the wall) at the completion of the throw. A good passer must develop a considerable amount of wrist snap, so to be very conscious of this as you work on this drill. On all of the passing drills, strive to improve your accuracy by always throwing at a definite spot. If you are throwing to another individual 15 yards away, aim for a spot such as his nose, or his right shoulder, rather than just throwing the ball in his general direction.