Unlike a real interview, you don't have anything to lose. Your purpose is to learn, not to score a job. The easiest people to get in touch with are people you know, of course, or people you are referred to. But cold calling is an option, too. If you come across someone impressive at a conference, in an article, or by reputation, try calling or writing to him or her.
People love to talk about themselves.
I repeat, not - a tortuous experience. Unlike a real interview, you don't have anything to lose. Your purpose is to learn, not to score a job. As long as you have the questions, your interviewee is the one who will do most of the talking. Keep the interview brief unless your interviewee is willing to take extra time out of his schedule.