Simple situations to promote thinking
Teaching Guidance for 14-16
Choose very simple situations to think about interacting systems
Choosing apparently simple situations to promote discussion can result in a clear understanding of what interacts with what, and how to model the situation. The essence is to learn to see a new situation in terms of one with which you're already familiar.
Promote lots of discussion about simple systems, asking how they can be redrawn to make them more familiar.