I also started every class with a question/answer period. The rules were simple, the questioning will last at least 10 minutes, and you don't want me to ask the questions. :-) Anything that had come up in the questions that seemed to be a point of confusion was sure to be added to the next homework set.
I won't go into what else I did with that class, but the end result is worth thinking about. First note that I gave a ridiculously hard final. Other grad students who saw it thought that the class would bomb. Secondly they aced the test. What do I mean by aced? Well I had a bonus question which fellow grad students thought nobody would get. 70% of the class got that question, and a good fraction were over 100% on the test. So they must have studied hard, right? Nope. I ran into some students several months later. They told me that they tried to study for the final and stopped after a few minutes because it was useless, they knew everything. And several months later they still knew much of the material cold!
The thing is that none of what I did was very radical. The principles have been known for a century. Psychologists have been trying to get people to listen for that long. I learned about it in the 80s from a university course I watched on TV. (British Columbia had a TV channel devoted to lectures for correspondence courses.)
Yet, despite how dramatic the effects are, nobody listens and nobody takes advantage of it.