A simple trick to encourage lecture participation

It's the time of year when teaching is very much on my mind. In an essay about his teaching style, Michael Scott says something about encouraging student participation that stuck with me:

I’ve found that the very first class period sets the tone for the whole semester. If I don’t get students to participate on day one, they probably won’t participate at all, and the course ends up dreadfully dull. My first lecture in any class thus begins with a brainstorming exercise, in which I get as many different students as possible to voice a suggestion or opinion. 

Last year I tried something like this in my undergraduate machine learning class. I don't want to go into details in case I use it again, but it wasn't a brainstorming exercise (I couldn't think of one), but a simple quiz question that introduced part of the material. I had the students vote on the correct answer---and everyone voted wrong, because it was of course a trick question.

To my delight, I found that year's class asked many more questions than the one before, even though it was significantly larger. This may be due to random variation, or to the fact that I was better at teaching the course the second time, but it's enough that I'll keep trying it.