This is what I have done when I teach.
Make the class fun but set the ground rules right up front so all will know.
Have all your students turn OFF CELLPHONES . This is annoying to all and just plain rude.
Have good step by step samples made for every foot....Use different colored thread in bobbin and top,this way the students can 'see' what you are teaching and talking about. Pass the samples around.
Label everything with your name,things get misplaced very easily.
Have a good supply list for the students ,include paper and pencil for notes.
Make sure the sewing machines are in working order,you are mechanic and it is not your job to fix the machines.