Let me tell you about a guy I know. He started out in affiliate marketing a few years ago, and didn't have a clue what how to make money. He started from square one. Not knowing any better, he opened an Amazon affiliate account, put up a simple website, and ran some pay-per-click ads.

Did he get rich?

No.

He didn't make much money. But he made a little. And he was hooked. He got deeper and deeper into the world of online marketing. He learned, and studied, and experimented. And year after year, his online income grew. But there was trouble on the horizon...

Sounds interesting, doesn't it? Wouldn't you like to see how the story ends?

Sure you would. Because stories are one of the most effective ways you can communicate with your prospects. Stories illustrate the point you are trying to make, without bluntly coming out and saying it. Telling stories helps copywriters avoid the trap of relying on statistics and numbers - because those are boring. Stories are interesting. They play on the reader's emotions. And they keep the reader hooked, because they want to see how the story ends.

Stories make great sales letters.

So, what do you need to write a story?

A Hero

This is the person the story is about. You can use you own experiences, or the experiences of someone you know, or someone connected with the product (like its inventor). Don't lie, and don't fabricate. If your product is good enough, there will be plenty of heroes available.

Conflict

There needs to be a challenge, or a loss. There needs to be trouble that seems insurmountable. That conflict can come from within the hero, a battle against himself...or it could come from outside, like a mean boss or a ruthless competitor. In sales letters, the best kind of conflict comes from how competitors product failed to do the job, causing stress and hardship. Or it could come from your protagonist's own disappointment and lack of success in trying to solve his/her problems - without the aid of your product. Stories have a resolution. There needs to be deliverance, or redemption, or success. And your product should be tied to it in some way.

Great stories show, they don't tell. In other words, don't say "The young man cashed his check." Instead, say, "The young man entered the bank, and confidently strode to the teller. He could not help but smile as he handed her the check. The teller's eyes widened as she saw the amount. She looked up at him. His smile grew wider. "Yeah," he said. "I know what you're thinking. But that is the correct amount."

See what I mean? Describe the nuances of the scene as vividly as you can. And as you can see from that example, you don't need to use any numbers or any boastful language to make an impact. Describe the conflict through actions, dialogue and consequences. And don't forget the little flourishes and details that make the story more engrossing. Be excited about your product, and make it the real hero of the story.
But a couple of words of warning.

Don't be negative about your product.

Don't suggest something that causes readers to digress from the main point of your story. You want to keep them on track. So that means no clever puns, no jokes, no double entendres. Those get distracting.

And no political comments. Those alienate readers.

Just tell an interesting, engaging story in which your product ultimately saves the day, and you will be sure to have a happy ending.