While this is not really a Moodle issue, it is a common teaching issue. I am going to advise that the best, for me anyway, is to introduce yourself, defining your expertise, and ask one person to do the same, then another and another until everyone has responded. Also, you might want to ask them why they are doing your course if they are choosing to do it, not if it is compulsory. Look for common ground amongst them and try to build on that, if they are adults. During your first few sessions, if it is, say, a week long course running two sessions a day, look for ways to create small group activities with the material you are trying to teach. You can swap members of these groups every time so that everyone gets to work with everyone else. We all eat, so if adults, share food and break times. Find the ones who do not join in and encourage them to do so, invite them specifically to a table. Do things that suit your audience.
Of course, if children, then they are likely to have shared classes for a while, so all the above is either not useful or inappropriate for the student-teacher relationship. You haven't said, but by the tone of your question, I am assuming adults who don't work together and don't know each other.