When doing an interview, you need to do a few things every time.
Fill the frame
When doing an interview, you must carefully choose good composition and background. Pay attention to everything inside the frame.
Get tight on the person you are interviewing.
Kill the Noise
Once you put the microphone in place and have your headphones on, you can hear all the ambient sounds. This is where everyone is quiet for a moment while you listen.
Let’s say you hear the ceiling fan or the air conditioner running. I would turn these off for the interview.
Move to a quiet location if you cannot turn off something like a water fall or water fountain.
Steady the Camera
Use a tripod or put the camera on a table. Just keep your primary camera for the interview still. If you have a second camera to use, you can maybe put that camera on a slider or fluid head that will let you move the camera during the interview.
I believe you always need one locked camera on a tripod for the interview.
Light the Subject
I suggest finding a great place with light, so you don’t have to use lights. I find the open shade on the side of a building works as well as porches, as you see in these two photos of interviews we were doing in Togo, West Africa.
Audio is King
There are times for different microphones, just as for additional lenses. You need to know the difference between a lapel, camera & shotgun microphone.
Sharpness is Queen
Sharp focus is critical. I advise against shooting ƒ/1.4 for video unless this is your second camera perspective. Have a depth-of-field that is forgiving if the person moves during the interview.
Use manual focus and not Auto-Focus.
Lock Down the lens
Don’t zoom in and out on your primary camera. You can do some of this with a second camera, but be sure at least one camera is locked down, and you have a solid framed shot that is in focus and has enough depth-of-field that the person can move a little and still be in focus.