The document at http://confluence.atlassian.com/display/JIRA/Migrating+JIRA+to+Another+Server does not specifically handle the use-case of maintaining a staging server. For example:

1. Disable mail handlers
2. Pointing any applinks to other dev instances
3. Recommendation to change the color in the UI, so staff know they are on a dev server
   You may also wish to use a custom icon and favicon, preferably ones that are brash and "in your face".
4. Where to get a dev server license

Also that doc talks about upgrading.

UPDATE:

The Migrating JIRA to Another Server document is not the correct page for this doc task.

The instructions for creating a staging server are documented on Establishing Staging Server Environments for JIRA.