[Andy]

Identify the setter and her "opposite" player. In each rotation, these two players should have two other players between them. Know where your setter should be on each rotation so you can easily look at the players on the floor and see the setter and her opposite player. If there are not two players between them, then someone is out of position and/or overlapping.

Another thing that I have seen for the last several years that, IMO, does not get called enough. In a serve-receive, the setter is in the center back position and is up near the net behind the center front player. The other two back row players will want to cover the back part of the court and may move toward the middle to better cove that open area. By doing so, they may overlap the setter who is up near the net. Usually, you can use some of the painted lines on the court to help "see" this overlap.