Some tips for writing a short funny story are to use the K Rule and the Rule of Three, and use them both sparingly. Words with a k sound are perceived as funnier than other words, and their usage is effective in subtly or subconsciously amusing readers. The Rule of Three establishes a pattern with the setup and then redirects the reader with the punchline. This can be done using two similar ideas and then adding another conflicting idea.
The K Rule is useful when naming things or characters or when word-crafting. Also, hard g sounds are subconsciously recognized as being almost as funny as the k sound. When employing the Rule of Three, a writer can use two humorous, but less important, ideas, and then reveal the punch, or point. These rules, as with other humorous conventions, should be limited to selective references. Keep the purpose of the story in mind; do not allow humor to distract from the story's main point.
Write about something familiar. Hook a reader by adding detail, color and flavor to the story. Be specific in the detail; a story in which the reader can picture the scene through specific detail tends to be funnier than a generalization.