Stay away from bright light sources such as windows when you are shooting inside. Video cameras can't handle the contrast very well and trying to light to match the sun will wash out what you are trying to shoot.
Use three point lighting. This is what professionals do. Use a key light to light your subject from the front. For a person, light the main side of her face from a bit above eye level making sure you light her eyes. Use a fill light on the other side. The fill light should be enough to keep the subject's face from being in the dark but not overpowering. Use a backlight somewhat behind the subject and off camera to soften the lighting.
Bounce and mask lighting to avoid shadows. Whenever you use unnatural lighting you are going to wind up making unnatural shadows. Move the lights around somewhat to minimize shadows. Use big pieces of white cardboard to bounce light indirectly, which will help cut shadows down. Use colored see-through plastic to filter the light. You can buy these from camera stores. Professional lights have places to hold these kinds of masks in front of the light. Use some kind of a stand to hold the plastic sheets in front of the light if your light doesn't have a place to hole them. Be careful not to use material that can burn such as ordinary paper.