1.Confidence---You answer all the incoming questions confidently,do not blabber.Hear minutely and be specific.If you do not have any answer for any of the questions of the interview panel members,then show your ignorance politely and with positivity.Do not exert yourself and stretch unduely which tantamounts to negativity.

2.Calm----If they irritate you by questioning irrelevant questions,do not show any frustration.I have experienced that sometimes a few members of the panel do it deliberately. you have to take the same in right stride and defend with your courage without losing your coolness.

3.Care--While giving replies,you first induce your thought process, transmit the same in your verbal language in silient mode and when you are sure,then deliver.This technique is known as Mental and Speech Confluence.
It is not very simple to learn on immediate basis,but you will be able to master this postulate, once you attend couple of interviews.

4.Caution--The most important facet that you must deprive yourself from all your over smartness and not to answer superflously.They will be irritated without any inkling because they are so veterans that you won't be able to judge this. You answer with conviction and with all integrity.

If you can follow these techniques,I do not find any reason of your failure.