The answer to this question depends a lot on what it is precisely that your introduction to the edition of this play that you are studying says. However, I will give you a few ideas that I use to promote class discussion and hopefully this will help you expand discussion in your own classes.
1) You might like to go through the introduction and pick out any controversial statements, or thoughts that invite a response or debate. You can use these as debate topics to give to your students in groups so that they have to prove or disprove the statement based on the information in the play. Not knowing what introduction it is you are refering to, I can't give you an example from your introduction, but an idea you could use would be something like: "Caliban is a misunderstood individual who is exploited by Prospero." The kind of statements that work best are one's that can be supported and refuted by the text.
2) A second way of expanding class discussion based on an introduction would be to divide it up into four sections (or so) and then give each of these sections to four groups of students. Their job is to study their section and present it to the rest of the class in a creative way. It could be in a drama or a poster. They have to conclude by giving their thoughts about the section they have analysed, pointing out the sections they agree with and disagree with and their reasons. Then each of the other groups has a chance to respond.