It is only after the first pass through the person's narrative that you begin to ask clarification questions that focus upon areas of particular interest. Learn to be a good listener. Unfortunately, this excellent advice is not as easy to do as it sounds. Most people are much more visual than they are auditory, making this a difficult change to make. What does help is the consistent use of silence.
People tend to fill silence with conversation.
Since you want information, it serves two useful purposes. First, it forces you to listen and assess the information. Second, the more the subject is allowed to talk, the more comfortable and candid he or she becomes. You can also encourage the person to talk by using common conversational ploys. The questions should be kept simple-not long or complex.