This idea is the product of two observations that I had. The first observation was of a science teacher. The second observation was of my correction of her mistake in a different lesson altogether. I need to give you a little background on what her group project was.
For their science project, they were given three different small objects, a simple balancing scale, and various weights with their measurements listed in grams on them. There were about 3 to 4 students to a group. Each student was supposed to take turns trying to balance each of the three objects. To be clear, they balanced the objects by putting the small objects to be measured on one side and some number of weights on the other side. Based on how many weights were on one side, they could arrive at a rough estimate of how much each small object weighed in grams.
Did you notice that I said that they were supposed to take turns using the scale? They had some difficulty with that. Several groups had difficulty with taking turns because they were quarreling over who should go first. I would estimate that some groups spent at least 5 minutes complaining and quarreling about who should go first. This problem occurred because the teacher did not give them a way for deciding the order that they should go in.
I observed another group project. Each group consisted of 4 members. Each member had to take turns applying a single rule in order to guess a mystery number and identify it on a 8.5 X 11 hundreds chart. When I walked around to each group, these were the first questions that I asked: "Who's first? Second? Third? Fourth?" Then, after we agreed on the order, they proceeded as such. Unfortunately, "agreed" on an order was really me just telling them the order that they would go in. Ideally, I'd like them to be able to independently decide their order with little or no fuss. Anyway, the bottom line is that they started out a lot smoother than when they were left alone to bicker about the order.