I find that when I am studying something tricky (weird or new math), outlining as I read helps a ton. I almost never refer back the notes later, but the act of

I find that when I am studying something tricky (weird or new math), outlining as I read helps a ton. I almost never refer back the notes later, but the act of trying to write something down intelligibly forces me to make my high level understanding explicit and prevents me from glossing over important details. To some degree taking notes during a lecture did the same thing for me when I was back in college.