we were given 20 min for each discussion and the guys in my group made it like a fish market.
in group discussion one should be calm.if u get first chance to speak well n good otherwise listen to others completely.never try to cut your fellows.but as in my case i tried to speak many times but the guys didnt want to listen in urdu dicussion.but i managed to speak twice.english discussion went very well.
few tips

be calm and relax
try to be the first one but if u dont be the first one.never mind.
listen to others carefully
support your fellows.
speak wit reason
dont beat about bush,


in command task we are not asked to give designation.
you r the boss there.so behave like that.neither be arrogant nor sheepish.just be confident and be yourself.
time management is most important.
also include suggestions from ur fellows in ur decsion.