Effective listeners remain focused and actively try to absorb material. Aggressively tackle difficult material. When they encounter a tough topic, poor listeners absorb very little. Things bounce off them. Effective listeners condition themselves to be interested in challenging matters.
Poor listeners tune people out on the basis of a few words.
Get to know the professor personally. Poor listeners see a professor as a talking head. Understand and use the differential between the speed of speaking and the speed of thinking. We think at about 400 words per minute. That's four times faster than most speakers can talk.