The author acknowledges the difficulty of getting valuable information from talks and likens it to being thrown off a horse. They introduce the “Three Things” exercise as a way to overcome this challenge and get more out of seminars. The goal is to have three specific takeaways from each talk, such as a definition, theorem, example, problem, or question. The author suggests writing these things down on a clean sheet of paper or index card during the talk. Afterward, participants can share their three things with others for discussion. The exercise is meant to enhance the learning experience and encourage further engagement with the material.
https://math.stanford.edu/~vakil/threethings.html