Much can be learned about a good lecture by observing Michael Sandel, a Professor of Government at Harvard whose course, "Justice," regularly enrolls more than 700 students. (2 minutes 30 seconds - YouTube video)
PM - Look at the size of the lecture theatre! The video looks really dated, but the way the session is run is amazing! Nice to see a 'flipped classroom' mode a few years before they became popular in educational discussions.