It is very important to listen to every idea that is shared instead of thinking about what your next question should be. It is also important to acknowledge every idea and to try to make that idea fit into the total picture of the day's discussion. Students are easily discouraged by a perceived lack of enthusiasm or support on the part of the instructor. Be enthusiastic when students participate and be positive toward their ideas no matter how irrelevant they may appear to you. If your room does not appear to be conducive to discussions, request another immediately.
Discussion works much better if students are seated in a circle or semi-circle rather than in rows.
This puts everyone on equal footing with each other and with the teacher. Strike a balance between allowing for volunteers and calling randomly on students. Always calling on students stifles spontaneity. If a question is directed at the whole class and no one answers, reword or redirect the question, call on someone reliable, or make jokes about their lack of response in order to loosen them up. Instead of expecting someone to answer immediately, allow sufficient time for them to gather their thoughts.