Take notes.
Once the notebook is filled (or the semester is over) scan the pages, toss the notebook, and buy a fresh one for the next semester.
It works, from much personal experience You're welcome!
1. yes, sometimes I fall behind the lecturer taking notes, which can be a bit frustrating
2. while the notes may not be complete, they trigger the context of the lecture which works
3. reading my notes from 40 years ago - they don't make much sense, as the context is forgotten
4. I wish I had made audio recordings of the lectures. But that was impractical, as I could not afford the cassette tapes required