Caryn B. answered 06/08/22
Visual Art Teacher, and K-12 Reading & Writing Tutor
Before you do an entire scene, you really should know about high mid, and low ranges of light to dark values when you are drawing.
A common assignment is to take a piece of white fabric and arrange this in a curved or crumpled pile on a table. Then you can add a light source such as a goose-neck lamp or clamp light, pointed at an angle toward the fabric. You should really practice light and shadow as gradients on curved surfaces such as fabric if you are planning to do well-lit people in space next.
After you get confident with depicting light and shadow on lit fabric, then taking photos with people who consent to be a part of your project or free and fair use stock imagery is a great way to see the value scale on well-lit people.
If you are working with colored drawing material, using light to dark gradients of the color is best. You can tint the color slightly with the complementary color, instead of using black to darken shadow areas. Using black to darken colored pencils or paintings always makes for messy shadow areas. What materials are you working with?
Alternatively, if you are working with graphite or charcoal, using black and white photography is what lots of art teachers have students do. This way your lights and shadows are already translated to a 2D surface, and they are static, in greyscale.