You have to share your successful and unsuccessful interview techniques in a conversation. I can start the conversation with a few suggestions but you have to take from there. So here are a few commonly mentioned points about interviews.
The most successful interview has two interviewers. One takes notes and the other speaks. Don’t divide the speaking. The one who takes notes should rarely speak and then only because the speaking interviewer has forgotten something. The speaking interviewer tries to maintain engagement with the subject. The speaking interviewer tries to keep the subject talking as much as possible and on-topic as much as possible. That job requires the full concentration of one person. That person should not try to do other things at the same time.
Avoid recording devices. If you do use a recorder, make it one that is very easy to operate and not intimidating and leave it on the table between you and the subject. Invite the subject to turn it off if they need to
go off the record. You may want to turn it back on after the secrets have been shared. On the other hand, your experience may tell you that it has been inhibiting the subject or been the focus of the subject’s attention. You may want to announce that we don’t need it further and pocket it in that case. There is a balance, by the way, in the user interface of a recorder. It has to be able to tell you it is recording but it also has to fade into the background. Lots of recording devices, including one I often use, go too far one way or the other.
The most typical problem students have in interviews is that they fear silence. Can you allow enough silence to elapse to let your subject gather their thoughts? If not, what can you do?
Look puzzled. If there is too much eye contact, just write a question mark on your notepad or draw a simple shape like a circle or square and look puzzled again.
Look at artifacts. Any diagrams you generate in your interviews are artifacts that you can look at silently with your interview subject. Just don’t say anything at all and look intently at each artifact.
Ask the same question over and over. If the subject is reluctant to speak, just ask them to
say more about that.
Ask hypothetical questions. Activate the subject’s imagination by asking them to place themselves into a situation and say what they would do.
Allow the initial speech, then stay on topic. Experience shows that subjects have rehearsed a certain speech about whatever is bothering them. They have to be allowed to declaim that speech. If not, they will keep losing track of your questions as they seek an opportunity to insert the speech. Once that is out of the way, let them refer back to it but do not allow them to repeat the whole speech or to give the certain speech about another issue. If you interview a subject about something they would like to be different, the interview may trigger associations with other things they would like to be different. You may feel the need to express empathy and tell analogous stories from your own experience. You should rehearse any such stories beforehand so you can abbreviate them as much as possible.
Overtly display respect and appreciation for the subject. I may have mentioned the robotics team of undocumented alien high-schoolers from Phoenix who defeated MIT in 2005. (There’s a Wired profile of it that gets linked from various blogs every few months.) One of the key reasons they are thought to have defeated MIT was that, when they interviewed experts in underwater robotics, they treated the experts much better than did the haughty MIT team. One of the experts, interviewed by Wired later, said he gave them a lot more help than he gave the MIT team and that he began to think of himself as a member of their team. You can’t buy that kind of help.
Don’t bother to ask if a subject can think of anything else. Instead, stimulate them to think of something else. You can stimulate them by asking them about situations. When was the last time X happened? If they say something never happens, keep searching for that one time.