Well, a user story should represent something about the system being developed that is valuable to the customer.
Some people like to use a formal template for describing their user stories, e.g. As a (role) I want (something) so that (benefit). Using such a template generally helps you think about who (role) a certain feature is built for and why (benefit). Some people don't bother explicitly mentioning the role or the benefit. Some people just write a couple of words down and call it a user story. After all, a user story isn't intended to fully describe the feature but rather serve as a handle.
Have you read Mike Cohn's "User Stories Applied"? If not, I highly recommend it.
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus