Groupwork

First and foremost is you should be well prepared as to what you need to discuss. I think your question about the group discussion is based on the group discussion after the written exam and before the final interview. Then you will know the topic for discussion and be prepared with the topic. If needed write down notes of all the points that you want to put down during the discussion. If someone is interupting (obviously some one will interupt and that is why this group discussion is for), dont proceed further, wait for them to finish and after clarifying that question of theirs, you could proceed with your points. But if the question is bit out of the way for what you are talking, then you could tell them politely that you will answer them at the end of the discussion. While preparing for the discussion, stand in front of a mirror and talk looking at your face and then if possible record your voice and listen to it so that you will be able to analyze how you are putting your ideas and thoughts. Hope this helps.

Well, if the group is composed of individuals that I don't know, the more confident I would be to state around my opinions as well as be open with their retorts about my say. If the group is composed of people I know and would eventually fool around when I say something serious, I'd go along the side lines until I could tag along a conversation or discussion that they have started. Now, which confidence are you talking about in the first place? One which would enable you to attend the small group or one that would enable you to participate in the group discussion?