The best time to take coaching for CAT is January . If counted in hours you need to devote nearly 500 hours of sincere efforts for your preparation that means devoting around 1.5 hours per day would be sufficient. Even before joining the coaching you can work on your basics by doing self study so that when you take up coaching you can cope up with the pace required. Be consistent in your preparation as coaching can be a support system but what matters are your efforts.All the very best for your preparation!