Less text + better images = more retention
Read this good explanation of why text-heavy Powerpoints actual impede comprehension, and follow the suggestions to make them better.
"How do you ensure that your kids learn from your lectures rather than wind up with brains that feel like oversoaked sponges? ... Richard Mayer, a brain scientist at UC Santa Barbara and author of the book "Multimedia Learning" offers the following prescription: Eliminate textual elements from presentations and instead talk through points, sharing images or graphs with students."
For more ideas, check here.