Which rule needs to be remembered when preparing for a group discussion? read about the topic ahead of time. concentrate on one's own points. memorize important pieces of information. speak as soon as you have a new idea?

I believe the answer is: .Read about the topic ahead of time. 
The group discussion should be a place where each members could bounce up ideas and perspective of the current topic.
If none of them read the topic ahead of time, they wouldn't have anything to exchange, which make the whole group discussion become inefficient.