Reveal your characters with light. Illuminating people differently will project their qualities. In particular, changing the direction from where a light originates can model a figure in a variety of ways, each creating a unique specific effect.
FRONT LIGHT: Car headlights. No secrets. Let it all hang out. Projects a huge shadow behind. Character revealed.
BACK LIGHT(Directly or offset to one side)/DOWNLIGHT: Sunlight/Moonlight/Streetlight. Separates the character from their surroundings. Allows them to pop out and be distinct. No one melts into the scenery.
UPLIGHT: Unnatural direction. Burning sewer grate. Candle under the chin. Creepy. Monstrous. Beware the up-lit character.
SIDELIGHT: Room lamps. Sunrise/Sunset. Adds dimension. Fills out the form of your character. Depth, complexity. Brings out the folds in their clothing.
What type of light is catching your characters?