In a short story, only include characters essential to the plot. However, when creating these characters, the author must know much more about them than what is shown in the story. Develop each character before you begin writing the story. Know the basics, such as his name, age, job, appearance, temperament and marital status. Beyond that, delve into more complex parts of the character such as the things he loves, the things he dislikes and what fears and aspirations he possesses.
The character does not need to be described in full detail. Instead, the character's actions and dialogue paint a picture of who he is, allowing the readers to draw a portrait in their minds as they read the story. As a successful character speaks and acts, he should reveal himself to the audience. A fully drawn character isn't needed in a short story the same way it is in a novel. Consider it as offering only a glimpse of the character.
In a novel, writers have the luxury of filtering the action through the point of view of numerous characters. In a short story, limit the action to a single point of view. However, not every short story must be written from a first-person point of view. Instead, a close third-person narrative structure still allows you to use the point of view of your protagonist. When writing a short story, imagine how your character feels or will react to a situation.
Set out to define the goals of each character quickly in a short story. Both your protagonist(s) and antagonist(s) should have clearly defined interests to alert the reader what is at stake in your story. However, do not simply state what each character is attempting to do. Allow their actions and the thrust of the story define motivation.