If the light in a scene needs just a little adjustment -- bounce it.
This lighting tutorial from Lynda shows you a few helpful techniques for bouncing light in order to get softer, more even illumination.
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Bouncing light is helpful when you just need a little adjustment to the intensity of a light, especially if you're working in a confined space and can't move the lights further away from your subject. Pros use this technique often because it softens a subject's face by diffusing light to give them a more natural, even look.
Though it can certainly be used to light subjects, remember that it's also used to create atmosphere. Cinematographer Conrad Hall describes the light that is bounced off of walls, ceilings, floors, and other surfaces as "room tone," so it's important to pay close attention to not only what bounced light can do for your subjects, but what it can do to create the mood/tone/atmosphere in a particular scene.