In addition to Opening Questions (explained here on this site), author James Lang suggests that another way to tap into the power of retrieval practice is by saving some time at the end of your class to ask students - before they pack up and leave - to review what was talked about in class today. What were the key points?
Lang's suggests that one way to make this even more powerful is to give students time to write down those key points. After a few minutes you can ask some of them randomly to read what they wrote.
If you pose this question out loud before anyone writes anything down, then one or two of your more involved students might come forth quickly with their answers before many of the other students have had a chance to think.
Want to make this really challenging (and more effective) for students? Don't let them look at their notes when they either respond to your question orally or in writing. You'll reinforce what you've learned by forcing them to retrieve what they just learned.
These final few minutes of review are going to be much more useful to your students than you continuing to lecture up until the last possible moment. Students' minds are often "out the door" anyway in those last minutes so use those minutes more effectively by having them reflect on what they learned.
Lang, J. M. (2016). Small teaching: Everyday lessons from the science of learning. San Francisco: Jossey-Bass.