How to Perform an Effective Interview

 
Ask open ended questions, don’t give options in your question (i.e. was it this? or this? or this?). Keep your questions brief and then shut up.
Do a Pre-interview. When you don’t know the guest personally, this is the fastest way to get to know them and how the will sound in the interview.
Rehearse your questions so the come out of your mouth cleanly. When asking follow up questions, take a moment to say them smoothly.
Take Notes
Ask questions that get to the core of their experience and let them reflect.
To get more specifics, ask for examples and case studies.
Scheduling: Send reminders in advance
Give a good introduction of your guest for your listeners
Practice your segues , comments – cool awesome are not diverse enough
Do research on your topic
 
References: 
http://derekloudermilk.com/25-best-podcast-interview-tips/