Organizations spend the majority of their hiring resources on finding and screening external candidates. But when you need to fill a position, the most cost-effective and practical thing you can do is hire someone from within. In fact, most hiring in companies is done internally. Still, the internal interview is often thought of as something to check off on a hiring to-do list rather than a source of real information. If you already know the person, what else is there to learn, right? Wrong. When conducted well, internal interviews can provide valuable new insight into a known candidate.