You need to keep the questions open ended and try to get the person talking about themselves or something they are passionate about and make a relation to it so you both feel like you are relating with each other and the conversation is leading somewhere.
This is an interesting and helpful video.
[youtube]http://www.youtube.com/watch?v=QUE1GPSQWxI&list=UUznQwonpzuFdMzaTt7rgGEQ&index=7&feature=plcp[/youtube]