To secure good marks in the subject you need to study it regularly. Do not leave this subject to be covered at the last moment. It is fun to learn a subject yet requires to give you time to study it so you can get your concepts clear. If you start preparation early, do make a self-note; self-note making is a good trick to learn while writing. After completing each topic, make your notes and revise them again after completing another topic. Follow this cycle of self-notes making to get good marks.