It is important that you have a strong culture of engagement in your classes. If students know they will be asked questions throughout the class, students will have an incentive to do work or think of answers in anticipation of that probability. You have made the students accountable, which is an incredibly powerful force.
One of the best ways to achieve student engagement is to ask students about their own experiences. These are questions that do not carry the pressure of getting the “correct” answer, and is a topic that the students should be most familiar about, their life. Using these answers can help students contextualize difficult topics. Showing how topics can fit into situations in their life can be the difference between understanding at a surface level, and truly internalizing topic knowledge.