Communication is not only verbal, but also non-verbal:
you should ensure that the signals you are giving out through your body language are positive, confident, and engaging.
For example, making eye contact with students/participants when you are talking to them shows that you are being supportive and attentive. As you teach, you should use gestures to emphasise your words. This increases the interactivity of the lesson, making it more visually interesting and hence, more memorable.
Moving around the classroom/group while you teach can help to remove the barrier between you and your students/participants, and gives them less opportunity to zone out or get distracted.
Body language is also important when dealing with negative behaviour. To avoid being confrontational, ensure that you don’t stand directly above or in front of a student, point, or invade their personal space.