Good ol handy highlighter does the trick for me. My review books, as most do, has a section of drills in the back of each content chapter. If I don't get above 5/7 I am not comfortable with the topics yet and therefore do more review and problems.
Generally people get tied up in trying to find weaknesses in themselves where they are easy to spot. Maybe first take a practice test. Going through you'll feel where you lack. If you scores are low in PS, start there. Personally, physics is my downfall so I spend most time there. I do not focus as much on bio and ochem as I have scored constant in these topics.
That being said....do NOT slack or stop reviewing a topic because you aced it. It's amazing what you can lose with confidence and a month of no review.