Just read through the driver's manual and make note of any hard numbers that it presents - like blood alcohol level or stopping distance, etc. For the most part the questions on the exam are pretty obvious but they do throw in a few questions that are harder and specific, hence I mentioned to pay attention to any hard numbers in the drivers manual.

I believe you only need to pass 70% of the exam and when I did it (many many years ago), the exam would just stop once I got 70%. Don't worry too much about it. You are getting a learner's permit so you aren't expected to know everything - just enough of the rules of the road to be competent.