In fiction, a reaction shot is a brief portrayal of how your character reacts to something that someone else has done. In contrast to more direct character building, your guy doesn't initiate the sequence; he completes it. Exactly how he completes it can tell readers a lot about him.

Novels have much more space than short stories, which gives you more leeway with the number of characters you can include. Even 'furniture' characters can be described and given speaking parts to develop background or atmosphere.

Overpopulated fiction can be so confusing that readers put the story down. Under-populated novels can seem claustrophobic or boring. You want the right number of characters for your particular work.

Nancy Kress Quotes