Basic Three Point Lighting for Interviews
You will use three lights: a key light, a fill light, and a back light.
Start with your key light. The key light will be your brightest light. Place the key light in front of the interviewee about forty five degrees above their eye line. Direct the beam of light towards the person's face. Watch the shadows on the interviewee's face. The nose should cast a shadow that doesn't stretch across the cheek and doesn't stretch down to the top lip. The nose shadow should just darken one side of the nose (you pick which side.) Now expose your camera to the key light on the interviewee's face. Basically that's the key light set up. One other thing to be aware of is the glint of the key light in the interviewee's eyes. You want the glint. Don't move the key light so far in any direction that you lose the glint.
Now set the back light. The back light should relatively be the same strength of the key light. If you have a 1000 Watt key light use a 1000 Watt back light. You want to start by setting the backlight up behind the interviewee, exactly opposite of and diagonal to the key light. The back light should now be set up, but you can always move it to your liking.
The fill light should be half the strenght of the key light. With 1000W key light, use a 500W fill light. Place the fill light in front of the interviewee on the opposite side of the key. If the key is on the right hand side, place the fill on the left hand side. To brighten or darken the intensity of the fill light, you can move it closer or farther away from the interviewee.
Moving any of the lights closer or farther away from your subject will brighten or darken its intensity. The brightening and darkening of the light by moving it closer or farther away is based on the inverse square law. The inverse square law means that if you double the distance between the light and the subject, the light's intensity will be quartered; if you halve the distance between the light and the subject, the light's intensity will be multiplied four times.
Now check your exposure one last time, and you're set.
That was one more piece of information you've always wanted to know! Now, go experiment and pay attention to how light interacts with everything around you - and pay attention to how movies and television shows are lit. With every project you will get better and better.