Develop Your Protagonist
Your story needs a dynamic, but realistic main character to drive the action forward. To bring your protagonist to life, think about what your character wants and his course of action to get that wish. Think about what he did before the story opened, and then start your story with a scene that shows him engaged in an activity that reveals his primary goal. For example, if your protagonist is a businessman who wants to secure a promotion, start with a scene that shows his meticulous nature. Show your protagonist as he polishes his shoes, straightens his tie, fastens his cufflinks and then flicks a piece of fuzz off the lapel of his expensive suit.
Craft the Conflict
Your main character might have a goal he wants to accomplish, but the story won't engage the reader if something isn’t standing in your protagonist’s way. To add drama to your story, insert a complication the character must overcome before he can achieve his desired outcome. While the complication often comes from the antagonist -- the character who wants to thwart your main character's goals -- the conflict can be internal as well as external. For example, your businessman might struggle with the insecurity and self-doubt that had held him back in the past, or you might develop a rival employee who wants to spread a nasty rumor about your businessman simply to smudge your protagonist’s reputation.
Round Out the Plot
Your story should have a chain of events, which includes a clear cause-and-effect relationship that raises the tension in your story and also raises your character’s stakes. Short stories are intended to be read in one sitting, so the sequence of events needs to move along seamlessly without too much background information, description or unnecessary dialogue. Select meaningful details that pique your readers' interest. In the businessman’s story, the plot might include scenes in the character's workplace that show the antagonist spreading his rumor and the protagonist becoming more anxious about his upcoming interview.
The Protagonist Makes Significant Choices
The climax usually occurs when the main character makes a crucial decision about his primary objective. At this point, the character should undergo a significant change in his values, motives or beliefs, resulting in a choice. His decision should logically stem from the story's events, but the outcome should also surprise the reader. For example, during your protagonist’s interview, his boss might ask him to explain the rumor. Realizing how easily the rumor has ruined his character, your protagonist might choose to quit his job rather than try to get the promotion.