Know first the person you're about to interview with. After identifying the things that you know about the person, you can start by asking things that they are uncomfortable with. Then you can see their personality towards uncertainty.
I can give you a few tips for I had to make some interviews to complete my thesis in high school. First, be prepared. Don't go unprepared.. Of course. Do some research about your questions especially if you're dealing with scientific subjects.
Second, write a list of your questions. Read them to yourself and try to answer them to be able to see if they're actually answerable or sensible.
Third, if you're going to interview in person, make sure that you're properly dressed, professional-looking and confident. This will affect the way your interviewee answers. They're more likely to participate well if you keep these in mind.
One thing you shouldn't forget is to write down the answers you get ACCURATELY. That's a must. You can get in trouble for putting words into someone's mouth.
There are two kinds of interviews from what I know about it. Fixed interview and impromptu interview. If it's a fixed interview, there is a way to go about it in order to get the best information on what you want the interview for.
First, you need to schedule for the interview with the person who you wanted to interview. Draft the questions you intended asking and send him a copy of it, so he can prepare for the meeting.
Make sure you are on time on the day of the interview, so that you can settle in well before the whole stuff kick off. Always ensure to stick within the frame of the questions you sent a copy to the person being interviewed. This will make the individual not to walk out on you because of bringing up what he or she didn't bargain to make public knowledge.
If it's an impromptu interview, I believe anything goes as long as you get an audience with the individual you wish to interview.