Beware when your star employee asks for a salary review. It should raise alarm bells. They may be looking for another job, they may have already received an offer from a competitor or they may just want to test you out to see how much you really appreciate them.
Avoid most of this angst by insisting your managers have informal and frequent chats with their people on issues such as salary, professional development and career aspirations. These sorts of conversations should never be an annual event; they need to be ongoing and a major component of your managers’ job.