Make notes after you have understood the concepts and do a few questions from your textbook to reinforce what you have learnt.
Do some past paper questions and see if you really get what you have learnt. If not, ask the teacher or go back and read over your textbooks and notes to see if you have missed out on anything.
Before the exams:
Read over your textbooks and notes. Make dotpoint notes or read them aloud (it just depends on how you learn/remember things).
Do some revision questions (i.e. study guides such as Excel or past exam questions).
Repeat this process for any concepts/calculations which you do not understand.
NOTE: Even though this may be slightly tedious at times, it is necessary to do this if you want to do well in chemistry. If you are unsure of certain things in the textbook, it may be helpful to read textbooks like Excel or Macquarie in order to grasp a basic understanding of the concept and then return to reading the textbook. It is very important to follow the syllabus.