Closed Questions - give the questioner the control and are easy to make conclusions from but only provide on word answers, "what day was it" or "have you always wanted to be an accountant"
Ask open questions, be a good listener and probe for anecdotes
Open questions - "Can you tell me about your trip?" or "How do you feel about civil unions?" Once a source starts talking, try to keep them going by asking follow up questions, "can you give me and example?" or "what do you mean by that"
Qualitative questions - Questions that require respondents to make a judgement about something on a scale that you give them. To what extend do you think mobile should be banned on a scale - 1 2 3 4 5 - Qualitative questions can be very good for getting specific details but can be limiting
Prepare for your interviews, come armed with a basic list of questions you hope to ask. You should already know your angle and a have a basic understanding of some of the work/events the person you are interviewing has done.
Some example questions
Can you please describe your biggest obstacle on the road to your success and how did you over come this?
What were some life changing moments that shaped the person that you are today?
Make sure you get background information and try to get something interesting, historic or scandalous!
Try to make your questions interesting so that the answers will be interesting!!