Due Diligence is a company term for conducting an investigation into any number of employees, from professional managers to rank&file personnel, business practices or internal/external organizations. The special definition of due diligence would have a whole lot of meaning in the business environment where these investigations are being conducted, since it can and will have different interpretations based upon the details being investigated. Due diligence should be discussed within its surrounding circumstances, so to understand due diligence much better.
Due Diligence Checklist Template
Extra reading — http://www.inc.com/tools/due-diligence-checklist.html