Hi,
Everyone has there own method of studying. What may have worked for one person to get 99 may not work for you. I did 13 units when i did the HSC and received 96.55 and every weekend diligently wrote my study notes and reread them every weekend, so that my the time i got to the HSC, i had read the notes so many times that it was second nature to me. I was also one of those that highlighted key point in my notes in colours and as funny as this may sound, remembered certain information based on the colours they were highlighted.
That worked for me and it was a long term solution to good marks, it did not happen overnight and i had to work hard.
All the best!