Things You Should Avoid during your GD
Do not shout or raise your voice which sounds too loud for the environment.
Do not criticize the basis of religion/race/caste/etc.
Do not get personal with anyone.
Never ever try to bluff.
Do not stretch a point for too long - it can make a good point go bad.
Do not cut anybody in-between. Wait for their sentence to complete and then speak.
Do not tap your fingers on the table, or shake your leg or any other unnecessary movements which convey impatience or disinterest.
Do not employ double-meaning statements or jokes.
Do not put down anyone. In case you don't agree with someone's point, either ignore or counter politely by asking them to see it from another angle.