Repetition and rewriting my notes always helped me in any subject. When rewriting notes, I would make sure to create a list of questions to ask to the professor/grad student at the next class or during office hours. It is very important to do this within 1-2 days of the lecture or else you could forget all the details. This is very helpful in particular for science/math/engineering courses.
Theresa recommends the following next steps:
It depends totally on the person and the kind of information you are trying to retain. Fo eg. if it's a concept you are trying to learn, saying it out aloud or writing the gist of the information into bullets might help. Repeating a piece of information that I read as though I were teaching a classroom of students or discussing with someone helps me simplify the information/concept and remember it better. I have also used illustrations on white board or paper to help me remember certain things. If the information you are trying to absorb requires memorizing something, such as acronyms you could make connections to something that you could easily relate to.
Gayatri recommends the following next steps: