The best approach to study this subject is to first understand the concepts and then solve practical questions immediately. This way you will retain the concepts for a longer tenure and understand your footing on the subject. 

• Study Time: As per ICMAI rules and regulation, there should be at least 9 months of time gap from the time of registration to the time of giving exam. The reason behind this is, that a student should do a thorough study of all the concepts. Therefore, it is always recommended to start immediately after registering to the course.  
• Study content:  There are many books which are available in the market as well as various books recommended by ICMAI. However, from the point of view of exam and to conceptually understand the entire syllabus, Study materials given by ICMAI is highly recommended. Cover the ICMAI syllabus in detail and don’t indulge in any selective coverage of syllabus.