As a developer I would like to always work on well-defined stories with unambiguous goals and all required details to code the feature or do the change. As I didn't find any complete guide to write user stories showing examples, I decided to write my own check list.
When I first wrote this, I wanted to list all conditions which must be met to pull a backlog item into a sprint. If any condition isn't fulfilled, the backlog item shouldn't be included in the sprint. There some risks on this approach, so I currently prefer to establish a process to improve the user stories more than to create a guard mechanism.