A few candidates withdraw themselves during the discussion owing to the dominating nature of other candidates. This will ruin their chances of getting screened in.
If you have written a good story and narrated the story with clarity and confidence, you are half way through. However, you must show your competence in the group discussion too, whatever the nature of your group is.
If the other candidates are shouting, you can politely ask them to calm down and speak one by one. If they still do not listen, you should look for pauses in the discussion to quickly convey your ideas.
Finally, being a good moderator and directing the group towards consensus will enhance your chances of getting screened in.