When you need to write user stories for your team, you need to remember to make your user story simple and straight-forward.
To make it simple you need to make it short and to not complicate it.
You need to think like a user when you are writing the user story description. And always talk as a user.
You need to make it clear and to explain main the reason for the story. What is the problem that you are trying to solve exactly?
The Agile user story should describe only one functionality. If you think you have more than one functionality think to break it into 2 stories.
This sometimes important especially if your team from a different culture or different backgrounds. Also, try to make this a fun activity for your team.
You need to write the acceptance criteria so you can help developers to know your expectations. Please review this workshop for more on how to write a good user story.
You need to make sure to define the negative scenarios that you don't need to allow them.
You should write the functional and non-functional requirements and use cases that you need.
You may want to mention any performance concerns if it is applicable to your user story.
Describe the intention of this feature.
In some cases, you need to mention the impact of this user story to the other features that already implemented in your system.
This might be part of the negative scenarios, that you may want to mention the UX concerns after implementing this feature.