The biggest cause of mis-hits in golf is a result of an over-the-top downswing.
A golfer is said to be swinging over-the-top when the arms are swung down in a circular motion away from the body from the top of the backswing. The arms come down across the ball from an ‘outside’ direction (instead of from the ‘inside’), and the club thus takes an out-to-in swing path approaching the ball.
The ten conditions for an over-the-top-downswing
The following are an exhaustive list of all causes for an over-the-top downswing, and either one, or a combination of some of them, will result in a mis-hit.
(Unless a golfer has the superb athleticism and timing required to bring the club back to the ball from a shallow and inside angle despite a biomechanically poor backswing)