Practicing a lot of past papers and atleast starting the studying schedule 3 months before exams.
If there is enough time, before going through past papers, jotting down all the chapters and sections in the textbook and giving myself a "score" from 1-5 on how strong I am in each section. This helps to focus on weaker areas. Then do the same after attempting past papers. This time give a score on performance on each question in the paper and see if there are any common weaker areas. Thanks.