Look for a topic sentence near the start of the story that sets up the plot and action. This won’t always work; sometimes authors bury the lead. Often, he topic sentence will point to the main idea. Look for supporting details describing the main idea and support conclusions.
The main idea is the central reason the author wrote the story. Ask yourself this question after reading the story, “Why did the author write this?” Often times the answer will point you to the main idea.
Sometimes the main idea will be the moral or theme to a story. Morals are often consequences to actions made by the main characters in the story. An author might deliberately place a moral in a story; or, he could put it in subconsciously.
Make a big idea chart. Separate the topic sentence and supporting details from the rest of the text in a story.
Write your own story, separating the main idea from the rest of your thoughts. Write about a topic you’re comfortable with and know a lot about. Be creative and embellish the story with supporting details. Practice finding the main idea in stories or articles you read, in movies and in novels. The more practice you put in, the easier it will be to find what the main idea is in a given story.