Stay away from asking "leading questions," such as "Don't you think politicians use their power for their own gain?" These types of questions are hints at the answer or lead students to a specific opinion. Encourage students to think on their own.
Follow up a "yes or no" question with another question. Ask students to explain their answers or positions and to provide examples. Allow other students in the class to elaborate on responses as well.
Un-layer or dissect a complex question. Ask short, concise questions as a way to build more depth and complexity into the discussion. Ask only one question at a time so as to avoid confusion.