You should take it as your goal to start a sustained, interesting
class discussion pertaining to the readings.  You should have some
clear concept as your "teaching point" that you will convey to the
class through the discussion.

There are a few keys to leading a good discussion.  

1.  Make sure everyone's on the same page.  If you need to define or
remind people of some terms beforehand to be sure, please do.  If it
looks like people are talking at cross-purposes, be prepared to
interject and clarify things.

2.  Either ask some questions that you think will cause people to take
different positions, or make a controversial statement that you're
prepared to defend.  There's no discussion if everyone agrees.

3.  In the event of class consensus, be prepared to defend the
alternative position - or move on to another topic.

4.  If things are rolling along nicely, let other people talk.  Your
biggest success would be a discussion that runs itself.

5.  Don't try to cover too much.  15 minutes is a lot shorter than you
think.

One possible tack is to devise some activity that pertains to the
reading and use that as the starting point for discussion.  Or you can
stick with asking questions, and guiding things along.

If you want to run some ideas by me ahead of time, please do.

  Peter