Start as early as possible - The more time you will leave for revision the more benefit you will get from it. You will have to learn the importance of time management in order to do well in any competitive exam. This will leave enough time for you to revise the main topics for the exam.
Prepare an Effective Daily-Study Schedule - If you are doing self-study, it is very important to have a fixed routine and important to follow it without fail. Make a proper routine and keep track of your preparation at all times.
Fix Weekly Targets and Achieve Them - You go to coaching since they take regular classes with a defined syllabus so that all the relevant chapters are covered properly.
Be Positive & Confident - It is very important to remain positive all the time in order to achieve success. Prepare well and practice well. Do not overthink the result.
Refer to Standard Study Material - It is very important that you focus on quality rather than quantity. You should focus on going through one book more than once rather than referring to more than one book.
Take Proper Rest & Sleep - Studying alone may be stressful and boring at times and if you are not able to crack even the prelims of any examination it becomes all the more stressful.
Revise, Revise & Revise - Revision of the most important cog in the wheel of your preparation. It is not possible for anybody to remember everything by studying only once. Multiple revisions will be effective for retention as well as application.
Bottom Line: - Competitive Examination is all about strategy and proper execution and nothing else. This can be best done if you are preparing on your own. Coaching centers will not be for you alone but in self-study, you will be able to understand yourself better and study accordingly.