Simple startegy you have to follow if you have not enough time say 2 or 3 months, and you are attending all group of CS executive or CS professional at the only attempt, then you must need to study 10 hours a day with full flow.
Try the CS Foundations book available only as well in market.. Try to give the MCQ test online so that you may know where you stand and how much you are prepared for this exam... Most importantly you should move forward according to the CS syllabus ...