of course it can be learned - the whole consulting industry is based on projecting credibility. Think about it - brand-spanking-new graduates have to appear competent and professional to senior client managers, when what they really want is to be in a pub garden. Take a deep breath, believe what you're telling them and make sure you know it better than they do - when you're speaking, you're the expert.I once knew the CEO of a Fortune 500 company. Every single morning of his long and illustrious career, he would be dropped at the office by his chauffeur, take a deep breath and say to himself "Showtime" before he went in. He changed from being the 'family man' to the CEO instantly. It was remarkable.Good luck