There are techniques on how to get people to participate. You can also have student discussion leaders for the whole class or for small groups. And sometimes they can be assigned ahead. I was thinking of Hema's class with the police officers, and how she might want to assign certain people to be the group leader. Some will work better in different settings and some will work better with different individuals.
Every class has a personality.
Sometimes you can do something with that personality and sometimes you just have to work with it. And I might, in the middle of the class, change the way I am approaching a subject if it is just not working. Design you own on-line catalog. It's because the students usually design your own on-line catalog, but they didn't know you could do those features. When we did this with my Penn State class, I divided the class into four different sections.