I also provide some avenues for ease of contribution. See Favorite Classroom Strategies I have also designed worksheets that help students to progress, in the course of the semester, from a basic understanding of plot and character development, to more complex literary and cultural matters. Consistently, students have told me that these worksheets are one of the most beneficial tools for their understanding of the literature. Each time a student talks, he or she must give me back a penny. Once they're out of money, they must let others carry on the discussion.
Some students are glad to give up both pennies immediately, others are more guarded with their loot.
And of course, the more loquacious ones are digging in their pockets for loose change or attempting to call out answers even though they're out of money. I have also used this exercise in the middle of the semester as a refresher. I have also heard of people using poker chips in a similar manner. This time allows students to jot down ideas, collect their thoughts, or construct a thesis statement. Thus, when we open up the question for discussion, everyone has a response prepared, speaking becomes less intimidating, and even those who remain quiet have a greater stake in the discussion because they have committed themselves to an answer in writing.