Whether you are drawing in chalks or graphite or pastels, painting, or doing pen and ink, pay attention to where the light falls. It can really make or break a piece. When you look at anything, look at what is dark, and what is light, and pay attention to where the light is coming from. Make it a habit to notice.
Before you begin a scene drawn or painted from imagination, decide where the light is coming from. You can create a lot of drama and interest this way. You can convey mood, too, by deciding the type of lighting. Is it strong? Even? Shadowed? Diffuse? What color of light? Golden sunlight of late afternoon? Bright white of an office? Colored, as from stained glass? Soft and diffuse, as from a cloudy day?
Decisions like these can be a great way to add life to your work!