Ask a question that inspires a productive conversation. The best questions are neither too open-ended nor too limited. "Yes or No" questions halt discussion, and broad "What do you think about young people getting married?" questions also tend to discourage students. The best questions are open enough to have a few possible right answers, yet closed enough that people know how to approach them, and feel motivated to start talking.
If you’re discussing Romeo and Juliet, you may start by asking, "In what ways does the Friar err in his advice to Romeo? In what ways does he succeed?" This question will lead students in a productive direction without feeding them the answers.
Giving the students a few discussion questions to be prepared for before class can also give them more time to provide thoughtful contributions to the discussion.