Some of the techniques that I used to maintain a professional presence are: first, I make sure to be on time for a meeting or an interview; the second, I make sure to be prepared. This two could change everything. For me is important to the other person you are meeting with feel that you are comfortable and secure about what you are talking about. I remember at my last job one of my bosses use to have the custom of always have a few interviews with people when he has important meetings; So at the last minute he always ask me to cover him; is not that I can not do it, but like I said I like to be prepare.