Stay Confidential every moment. An interview is just like a marketing where you have to prove yourself that you are much valuable for company. And Confident is act like your weapon use to answer any type of questions in interview.
And confident comes from knowledge of yours about the company and about your job profile.
Or you can say that interview is just a chance to represent yourself and to show how much you are useful for that company. It just a conversation between you and HR of company where you have to prove that you can do it with confident words said by you only. Interview is just a little test of your to know how much you know yourself that it. As if stay not fake than it will much easier for us to tell about our self that what we are actually.