You Call That a User Story? Sometimes this topic drives me completely bonkers! There are far too many people who claim to have the silver bullet answer to defining and consuming the perfect story. Spandex approach, one size fits all, is almost always a BAD idea!

Research, Research, Research..: The most important thing most of the story writer do wrong. For writing stories you can not follow the formal requirement elicitation method always. Most of the time users will not be able to tell you what they but you need to find out. But how? First create the persona. Here you will understand the paint point that you are trying to solve. From the persona you will get for whom you are building and their goals. Then with the data collected from many user persona sit with your stakeholders (Product owners, Dev team). At that point the ideas and analysis will come into stories.
Make the stories short and concise: A story will be meaningless if you can not finish it in one sprint. So you need to make it short and precise.
Follow the three C’s of user story: The three C’s of user story is Card, Conversation and Confirmation. From the card where you are creating story, then having a conversation with the stakeholders and then confirm it with the acceptance criteria.
Agility is prime goal: Don’t follow your story blindly. If it needs change, change it, the best stories comes with iterations, not with rigidity.
Don’t be technical: User story document should not have technical details of “how a server will work” or “How a button will work”. It is a explanation of behavior not SRS or any technical document.
Create a priority and order: Generally each story should be independent to each other. But if it has a tail and keep them in order and of course set priority which story you want to finish first and which one you want last.
Why can’t we just write features or task instead : Users stories and tasks are different. User story is “What” and Task is “How”. User story describes a piece of functionality in the perspective of users and tasks are how you will deliver the story.

Seeking the Lost (Jonah 4:11)