Who are the key interviewees? How many do you actually need to interview? Can you interview all key players in one day?
Where will the interviews take place? If outside, will you be far enough from unwanted noises such as: vehicle traffic, loud individuals, birds chirping. Also, if you plan on using a shotgun microphone you’ll want to use a blimp. Using a blimp will damping the sound of wind.
If you plan on interviewing in a room, are there any windows that may cause issues, such as glares or unwanted light? How many lights do you want to use for the interview? Is the space large enough for all your lights and gear? Do you plan on using a lavalier microphone or a boom mic? If you plan on using a boom mic, you’ll need space to place either a C stand or a microphone tripod. Using the correct boom mic will also help reject echo sounds entering the mic during dialogue (hard surfaces contribute to this).
Are your interviewees dark skinned or light or both? You may need to add gels to your lights for different skin tones. Use 3200k for light skinned individuals, and 5500K for dark skinned individuals. If you use 5500k (daylight blue) light on a light skinned person, they may appear to look ill or sick. Warm the lights up by using a 3200k bulb. If you are using 5500k lights, just put a 3200k CTO gel in front of the light to warm the light. If your interviewee is dark skinned, they are better suited with a 5500k light.
What questions will you ask? Know what info you want from your interviews.