Confidence. Make your students feel confident and secure when asking questions or making comments about lessons. Give supportive feedback even when students are incorrect with their answers. If they feel safe in the classroom, their motivation increases. Make students feel like they have some control over their course experience. Set up choices that makes students feel like they have some power over their education, even when it doesn't really affect the class overall. Allow for student feedback. It will help you improve your instruction where you maybe don't see an issue, and it helps students feel heard.
