Fill Card

For those of you who like taking portraits, a fill card is a cheap, easy way to enhance your lighting. All you need to do is bring along white piece of poster board next time you go shooting (obviously, you will also need a camera, subject, and it's always nice to have an extra person to hold the fill card).

The purpose of a fill card is to reflect light to the side of the subject that is shadowed (filling in the shadowed area, hence, fill card)
The location of the fill card depends on how much light you're working with, where the light is coming from, and what kind of shot you're looking for. So mess around with it.