Most amateurs that I work with will typically try to use the wrong club around the green and leave the ball a long way from the hole. In doing so this adds strokes to their score. I try to help them understand club and turf interaction and using the proper club and technique to get closer to the hole. The amount of times I see a 58 or 60 degree come out instead of a pitching wedge or 9 iron still amazes me but we are working on it. The other part is helping them understand where to land the ball to get it closer to the hole. This has been even more helpful for me to keep working on it. Experiment with loft and stroke to become more consistent and your scores will start dropping.