First, think of a basic story idea. Then, introduce elements that seem normal but lead to a sudden change. For example, a trusted friend could turn out to be a traitor. Or a seemingly solved problem could come back in a new way. Make sure the twist makes sense within the story's context.
A great way to do it is to introduce an unexpected element near the end. Maybe a character who was thought to be good turns out to be bad, or a solution to a problem comes from an unlikely source.
One idea could be that the character who seems to be the hero is actually the villain all along. For example, in a story about a detective solving a crime, it turns out that the detective was the one who set up the crime in the first place to gain fame.
In this short story, perhaps Cinderella is a talented inventor in a steampunk - style world. Her stepmother and stepsisters don't recognize her worth. When the ball invitation arrives, she creates a magnificent flying contraption to get there. And at the ball, the prince is more interested in her inventions than her appearance. So she has to decide if she wants to be with someone who values her mind or if she should look for true love elsewhere.
One is 'The Lottery' by Shirley Jackson. At first, it seems like a normal small - town lottery event. But the plot twist is that the 'winner' of the lottery is actually stoned to death as a sacrifice. It's a very dark and unexpected turn.
Another is 'An Occurrence at Owl Creek Bridge' by Ambrose Bierce. A man is about to be hanged on a bridge during the Civil War. As he falls, he seems to escape and makes a long journey homeward. But in the end, it turns out that all of his escape was just a hallucination in the split second before his death. It's a really mind - boggling plot twist.
One is 'The Lottery' by Shirley Jackson. In a small town, every year they have a lottery. People seem normal about it at first. But the plot twist is that the 'winner' of the lottery is stoned to death as a sacrifice for a good harvest. It's a really chilling story that shows how blindly following tradition can be very dangerous.