I had come across a very useful and interesting way to take notes, the Cornell note taking system.
I really liked the philosophy of it and used it to take notes in some non-Math courses. Here's what you do, you divide a page into three sections, by creating a left margin, a bottom margin and the main area.
In the main area of the page you write the notes, in the left margin you write the questions that the notes in the main area is answering. In the bottom margin you summarize the overall idea of the notes on the page.
I found it a pretty useful way to take notes and also a good way to think about anything new that we want to do. Before doing something, we can ask ourselves why we are doing it, and after doing it we can reflect on our actions and think about what we have done and how it fits in the overall scheme of things.
With this note-taking method, we understand an idea in the notes from three points of view. The idea as expressed by the teacher which we note in the main division of the page, our own understanding of what questions does the conveyed idea answers and our reflection regarding how the matter discussed in class fits in the overall scheme of the course.
Also, note that since English is written left to right and top to bottom, the left margin is chosen to write questions. IMO, this is done since the questions answered by the notes are generally pretty short and the questions can be horizontally aligned with the notes in the main-divison so that it is contextually clear which questions are answered by which parts of the notes. The bottom margin is left for the summary because it relates to the whole page and how it fits in the context of notes on the other pages.