When conducting interviews for news, documentary and oral history it is important to guide the participant but also to let them tell their story without too much interruption. I always begin my recording by asking the participant to say and spell their name. This allows me to adjust my audio levels, place the microphone properly according to their speaking volume, and it gives me a record of the correct spelling for reference. Usually you want to make the equipment the least important element in order to keep the participant comfortable and appearing natural however, if you are including video in your finished product you don’t want to have sloppy mic cable placement visible within the frame. Ask the subject to place the mic cable under their shirt and find a spot on their clothing (button edge, jacket lapel) to clip your lavaliere microphone. Try to control the sound environment. Listen closely to the location when you arrive and be sure to turn of televisions, radios, and phone ringers as well as heating/cooling systems. Refrigerators and drinking fountains are noisy so you want to avoid locations with those or unplug them for the duration of the interview. Pets can also be problematic so try to contain them away from the location. If you are doing an exterior interview be mindful of wind and other background noises, trying to position the microphone so the subject’s back is to the source of the noise. In terms of equipment an external microphone with XLR inputs will give you higher quality sound. If you are working on a budget and are forced to use a built in camera microphone, a cell phone or some other consumer quality device get the microphone as close to the sound source your are recording as possible. If you include video this may force you to shoot the image in close-up but the sound quality will be improved. Built in mics often have AGC (automatic gain control) which will adjust the amplitude of the recorded sound automatically. For example you want the person speaking to be the primary sound source but the AGC might think the traffic noise in the background is important so it will automatically adjust to make the level of that source louder, thus the person speaking becomes too loud and it adds a lot of noise to the recorded track. Here are a couple of articles that will help explain AGC.
When I teach students I emphasize that anything automatic (focus, gain, exposure, white balance, and so on) is bad. Manual controls are preferable. That being said if you are on a budget get the mic close to the subject and try to control sound in the location.
I’ve conducted a lot of interviews during my career and you have to train yourself to not speak or respond during the participant’s response. In normal conversation we overlap our speech and say things like “really,” “uh huh,” “that’s interesting” and so forth. This is a habit you have to break if you are trying to illicit a stand-alone sound bite from a subject, meaning your voice will be edited out. Maintain eye contact, use visual facial gestures and behavioral responses to indicate to the subject you are engaged, interested and listening (raising eyebrows, smiling, nodding, etc.) This may not be as important for oral history but for film and video ask the subject to include the question in the response. If you ask them their name and they respond “Denise” that’s all you have to work with in editing and it won’t make sense. If they forget to include the question direct them and remind them and ask again so you get the desired sound bits; “My name is Denise.” Also be mindful of not overlapping your next question while the participant is still speaking. Try to record the silence in between questions and responses, this allows you to edit dialogue cleanly. Look down at your notes after they complete the response as though you are thinking about what your next question will be. Often times if you wait a little too long, participants might be uncomfortable in the silence and think of something else to say that’s better or more interesting than what you originally prompted them to say.
It is good practice to record an ambient track or room tone in the location. Sit in silence for at least 30 seconds and just record what the space sounds like. This gives you a track you can loop under the dialogue track to smooth out your mix. Audiences accept cuts between images easily however cuts in sound are jarring. Use crossfades on your audio tracks and J & L edits to transition sound changes gradually.
Here are a couple more articles on recording and mixing sound.
Lastly I always like to conclude my interview by asking the subject if there is anything else they would like to add or clarify. This gives them the opportunity to discuss things you may not have thought of and often times it gives you some interesting content.
Here are a few additional resources for conducting audio/video interviews.