PollsAfter you ask a few students for answers to a question you have posed, you can poll the rest of the class for their opinions on the answers they have heard. "Raise you hand if you agree with Mary. If you agree with Joe. If you think both are wrong. If you're not sure of the answer. Those who think they are both wrong, why do you think so...."
Including the opportunity for students to indicated that they don't know the answer, gives you some feedback on how many students may be lost.
This can be a great technique to start off a discussion of the topic.