Writing a story for a blog post can be challenging, especially when you have a word limit to adhere to. Here are some important points to keep in mind when writing a 400-word story:

Choose a single plot point

Create a strong opening

Develop your characters

Use sensory details

Keep the pace moving

Include conflict and tension

End with a satisfying conclusions

Edit and revise

Here's an example 

Title: The Lost Wallet

Opening: Sarah rushed through the crowded subway station, her heart racing. She had lost her wallet and her train was leaving in ten minutes. She couldn't afford to miss it - she had an important job interview across town.The opening should realistic and intresting which encourages the audience to read more.

Plot: Sarah retraced her steps, searching for her lost wallet. She asked strangers if they had seen it, but nobody had. Just as she was about to give up hope, a kind old man approached her. "Is this yours?" he said, holding out hr wallet.it should be apt and accurate.

Characters: Sarah is a young, ambitious woman who is determined to succeed in her job interview. The old man is a stranger who helps her when she is in need. should also describe her features like eye color, height , education ,work current status etc.

Sensory Details: The subway station is described as crowded and noisy, and Sarah's heart is racing with anxiety. When the old man hands her the wallet, she feels a sense of relief and gratitude.

Conflict and Tension: The conflict in this story is Sarah's race against time to find her wallet and make it to her job interview. The tension is heightened as the clock ticks down and she is unable to find her wallet.

Conclusion: Sarah thanks the old man and rushes to catch her train. As she sits on the train, she reflects on the kindness of strangers and the importance of always paying it forward.

Edit and Revision: The writer would have taken the time to edit and revise the story to ensure it is well-written, clear, and concise. 

Use active voice instead of passive voice can help keep the story moving forward. Active voice puts the emphasis on the subject performing the action, which creates a sense of immediacy and urgency.

Cut unnecessary details: Be selective in what details you include. Not every detail is necessary to advance the plot, and too much description can slow the pace of the story.