Lighting is important because it will make the video look better.
Below is a list of general ideas to consider when dealing adding lights.
Look through the camera to see the subject and the lighting as the camera SEES it and as your audience will see it.
If the camera has ISO and aperture settings you may need to adjust them to compensate for light changes.
Avoid using lights:
From below
Too little (under expose)
Too much (over expose)
EXCEPTION: When you want to set a particular mood (erg., scary scene)
There are several types of lights that you can use:
Sunlight
Office lights (florescent)
Clamp lights (if you are on a shoe string budget)
Light kit with diffusers
LED panels
If the lighting doesn't look correct:
move the lights around
adjust lights height, distance, and angle
add or remove lights
more blue than yellow lights
diffuse light source more
dim the light
use a barn door
If the light is too harsh (erg., shooting outdoors or sunlight from a window), use a bounce card (a white piece of foam cord board) to reflect and diffuse the light on the subject.
Match the light colors (erg., don't use warm (yellow) and cool (blue) lights together
If you need to travel, ensure that the light kit comes with a traveling case.
Use three point lighting when possible. As the name implies, it has three lights.
Every subject may require different lighting setup.
If you are shooting outside, be aware that the lighting may change based on the sun and clouds movement.
You can make some edits to adjust your lighting after you record but it is best to do what you can before you record.
To minimize glare on eye glasses, look through the camera and then:
raise light and adjust angle
move key or fill lights
bounce light of of ceiling if it is low and a light color but increase the amount of light since it has to be reflected
have subject to tilt head down a little
have subject tilt glass down a bit
Use three point lighting. With all of the other lights turned off, Imagine the subject is at the center of a clock and the camera is positioned at 6:00, then:
The Key light is the "key" light or primary light and is positioned at 5:00 or 7:00 and can be a hard light or a soft light (one with diffusion). Soft light is best from training videos. It should be angled down from the subject eyes.
The Fill light is the "fill" light or secondary light and is positioned at 5:00 or 7:00 (opposite the key light) and is softer then the key light and is used to reduce shadows.
The Back light is (as you expected) the "back" light and to separate the subject from the background and is positioned at 1:00 or 2:00 and raise above the subject. Avoid the light being cast into the camera lens.