How should you write a reference for your boss?

Usually supervisors / bosses write references for an employee. To write a reference for your boss to use when he/she seeks other employment, you would need to have knowledge and insight into what the boss's job entailed. You could also write strictly from the viewpoint of an employee evaluating the type of supervisor your boss has been when you worked under him/her. As an example of the latter, you could write: "Ms. Xxyyzz has always been willing to help employees grow in their jobs. She takes an active interest in the employees' continuing education, and is available to explain new concepts to employees, if needed. Employees feel she is approachable and cares about the employees and the company's future." You could give a personal example about how your boss helped you in a professional matter. Always keep your letter short, to the point, and enthusiastic. If you have nothing positive to say, though, I would decline to write anything. But again, employees usually do not write a reference about their boss, so I'd wonder why she/he is asking you to do this.