Adequate matter

You should have subject knowledge and be well aware of the latest happenings around you, not just in India but around the world as well. To be in a better position, make sure that you have in-depth knowledge on the subject. Subject knowledge is a pre-requisite while you are preparing for a group discussion because you will then have the power to steer the conversation to whichever direction you want to. If you can memorize some relevant data, it will be an added advantage.