If you really want to prepare for CS exams, then please clear that CS Course is a highly reputed course so your writing skills will play a major role in giving you extra marks in this exams. If you Attend oral coaching classes, seminars, then it will be really beneficial for you.
A professional course definitely demands something more than the regular courses but we should never complicate the process of preparation. The most simple and the best way to prepare for such examinations is by going through the study material, provided by the institute, thoroughly and following previous years question papers.
Try to get question papers of at least last ten years and start preparing according to it. It will help you to understand the manner in which the questons are being set and will also give you the idea of common questions which has been asked frequently in the previous years and could possibly come in the upcoming examination.
ALL THE BEST.