“When do you recommend I start working with my professors’ old exams that they left on reserve in the library?”
It might be wise to hold off for a little while longer before looking at old exams. Old exams are excellent for predicting what your professors’ exams will look like. Unless you have a large supply of them, you don’t want to waste these resources by reviewing them before you’ve learned all the material that they cover.
Between now and your “reading period,” I would recommend using exam practice products like flashcards (or similar hypothetical exercises) for the subjects you’ll be tested on. These flashcards will give you the black-letter law, explain the public policy behind the rules, and provide you with mini fact patterns to practice your application skills. Since they are arranged in outline format, you can review the areas you’ve covered up until now in each of your classes.
Wait until you get towards the end of the semester, and your professor is wrapping up the course (e.g., after Thanksgiving break), before you break out the old exams you collected during the first week of school.