I agree that an instructor is most successfull if he/she creates an environment where students feel safe to ask questions and positive discussion is facilitated by sking open ended questions. I have encountered some students who have very negative attitudes and often feel that it is difficult to stay on track and redirect when confronted with sarcasm and negativity. What other strategies can be used to manage the classroom, and guard against negativity, in addition to addressing concerns with students one on one?