Address: Assess the terrain and adjust. Upslope: ball ahead, weight back use less loft. Downslope: ball back, weight forward use more loft. Level: club centered and weight 50/50. A suitable address sets the player up to succeed and vice versa. In all stances, swing the club so the sole brushes the grass just ahead of the ball. If you actually brush, the ball will be struck solid.
Trajectory: Have a mental picture of the ball flying low or even rolling. Especially for higher lofted clubs. Many players picture a flight higher than the club or their set up allows. This results in the player attempting to create the pictured flight and a probable thin or chunked shot.
Concept: Many have the false idea that the club is to get under the ball resting on the ground. This idea causes a vicious cycle with the 1st shot chunked, 2nd thin etc... all in an attempt to find this mythical place "under the ball." Instead, the club returns to where it began, on the grass and from a back and forth motion. The loft sends the ball up, not you.
Swing: The motion of the club is critical. Too much attention to the club head solely can cause casting or a leveraged motion. With this motion, thin and chunked shots should be expected. Instead, swing the whole club moving forward rather than just the club head. I'll instruct students to swing and replace the whole club just ahead of the ball as it was addressed. This creates a very solid strike.
Fear: Players who have thinned or chunked a shot previously from any of the above topics are increasingly subject to the interference of fear while they attempt a pitch (Yips). It is very troubling but correctable. Especially if the player holds to a positive purpose throughout the shot. The club will follow a mind that jumps ahead of the current task. So stick to what you are to do as noted above.
The pitch shot can be one of the easiest shots with it's relatively slow club speed. But because of a poor address, a high mental picture of ball flight, a poor concept, a casting club head and or the interference of fear bad pitch shots can be result. Be assured they can be eliminated if you follow these simple and positive cues and fixes. If you do, your confidence will grow and we all know "Confidence is King".