Whether you are teaching a course to a class, speaking in a conference, or giving a presentation, prepare well and just remember that you are there to share your knowledge and to learn from others. Don't go with the mindset that you know more than your audience, or with the notion that you know less than your audience. With the former, you would become over-confident and likely sound arrogant to your audience and they would hate it. With the later, you would sound inept and nobody would take you seriously.