In my experience, studying the material before teaching a lesson, even when you are vary familiar with the material, allows you to be better prepared to present the course material with your own spin and personality.
When you know what you know and it’s ingrained in you, teaching with personality that will keep your students engaged becomes so much easier. Studying and looking over the material gives you the opportunity to bring your personal experiences and the course material together to tell a story instead of just lecturing.
