Hey arsh,
To make a group discussion grand successful one should keep following points in mind
1. Be a active listener - pay attention to what other are saying in the group discussion
2. Take the initiative - never wait for others to speak first, always try to grab that opportunity
3. Take care of dressing - be the simple and sober in terms of your outfit while having group discussion
4. Try to polite while delivering your views - never shout while appearing in group discussion
5.  Be accurate to your thoughts - always speak when you are pretty much sure of what you are saying
Hope these points may help you
Good luck!