Here are a few tips to help you with this preparation:
Ask yourself what your goals are in talking with this particular person. You are not here to fight or pick at old battles. You are here to listen. Similarly, you are not here to confirm what you already know (or think you know). Let them talk, perhaps you will get details you never knew before, perspectives you never heard before.
Prepare Your Interviewee
Instead of just sitting down and start asking questions, tell them exactly what you are doing. This will help create context for them and put them at ease for the interview. You should share with them why you have chosen to speak with them. Speak from your heart and be sincere. Depending on your relationship, be clear you are not here to judge, but to learn. Convey that you respect and are interested in their experience, that you value what they might share, and their life’s perspective. People may feel they will bore you with details you do not care about so take the time to address this head on.
Prepare Your Logistics
Time of day: Ask your interviewee their routine beforehand. There may be times of the day they are more alert or free from their various activities and your interview will be more successful if you are able to work with their schedule.
Location: Choose a quiet place where there are minimal distractions and, if you are recording the interview, that offers better sound quality.
Equipment: Charge your phone or recording device beforehand. Bring a paper and pen so you can note follow up questions without interrupting their flow.
Silence your phone during the interview: You would hate to have a deep heart-felt story interrupted with the ping of a text or call.
Placement of recording device: Place the recording device somewhere it can easily pick up sound and the mic is unobstructed. Then, forget about it. Let your interviewee forget about it. People get stiff and formal in performance mode if you keep reminding them they are being recorded. You want them to be natural in order to capture their real personality.
Prepare Your Questions
Have some questions prepared beforehand and some sense of where you want to go with the interview.