It may seem petty, but on the employee’s final day, make sure you revoke access to all of your computer systems as well as collecting any cards or keys that give access to your physical property. You may trust that particular employee, but over time, having a bunch of ex-employees with access to company accounts and buildings will create a major security risk.
Mark the Occasion
No matter the circumstances of the departure, organizing some kind of event to thank the person for their service and wish them well is a nice touch.