It still amazes me how instructors fail to vary their instructional styles for the benefit of students. I had a professor in grad school who was considered an expert who would drone on for hours about his subject. It was excrutiating.

I don't think it is possible to underestimate how important it is to be prepared in advance. In addition anything you can do to emphasize the expectations and put students at ease is going to be helpful. Sometimes it can feel like overkill. However, you almost can't over communicate.