Asking your supervisor to write a letter of recommendation for you is probably far more common than your supervisor asking for a letter of recommendation from you. Given the tenor of some supervisor-employee relationships in the workplace, a manager might be taking a huge risk in asking you to vouch for her. However, the simple fact that your manager asks you for your seal of approval is a testament to how she values your opinion of her performance. That said, consider the impact of your recommendation letter and provide information that you believe will be most helpful to your manager's job search.
Learn More About Your Manager
What you know about your boss may be limited to your current role. Ask your manager to tell you more about her background, and from that, you might be able to glean more about the reason why she supervises the way she does. Perhaps she was a technical expert whose leadership capabilities were recognized by a previous employer, and she joined the current employer as a manager. Did she receive formal training to develop her leadership talents, or was it purely on-the-job experience and her relationship-building skills that resulted in her promotion to a supervisory role? You needn't review her resume or quiz her about her entire work history, but if you know more about how she came to be in her current role, it may make writing a letter of recommendation easier for you.
More Than One Perspective
When you begin your draft, don't rely on your experience alone. It's likely that your manager supervises more than just you. During your tenure with the company, you surely may have witnessed how she supervises others. Granted, she may value your opinion over others' – that's why she asked you to write the letter – but to write a letter that will be well-received by your manager's future employer, you could do a disservice to her if you write from solely your perspective.
If appropriate, and without identifying other subordinates by name, of course, recall one or two instances where your manager's leadership capabilities shone. Describe instances where your manager resolved workplace conflict, or when she provided the necessary guidance for a team project without simply jumping in to do the work herself. Write about her technical skills, too, but if she's looking for a leadership role, focus more on her capabilities as a manager or a leader whose behavior employees emulate or admire.
Structure, Content and Flow
Your recommendation letter should be approximately three paragraphs. The first paragraph should explain your relationship to your boss, how long she has been your boss and the reason you're writing on her behalf. Don't say you're writing because she asked you to; explain why you accepted her request that you write a recommendation letter. For example, you could begin your letter with, "I am writing on behalf of Susan Smith, who is a candidate for the manager position at ABC Manufacturing. I currently work with Susan at XYZ Contractor; she has been my manager for three years. "
This letter of recommendation should explain why you think Susan is the best candidate for the manager position at ABC; for example, "my experience as one of her direct reports has been immensely rewarding and she is one of the reasons why I enjoy my work so much."
In your second paragraph, relay a couple of anecdotal references which illustrate Susan's leadership capabilities. Refrain from disclosing sensitive information about your employer or other employees. Describe instances where she has aided in your professional development and what you learned from her.
For your final paragraph, if you're sad to see your manager take another job which would end the relationship that you currently have, say so, and be honest about it, but not overly sentimental. This is, of course, a professional reference, so even if you have a friendly relationship with your boss, keep this letter strictly professional. Her prospective employer wants to know how others view her skills and qualifications – not whether you have a great friendship.
Review the Draft with Your Boss
Before you send the recommendation letter to the prospective employer, ask your boss to review the draft. Double-check to ensure you have the correct addressee and contact information. After your boss has a chance to review it, you can refine the letter, make any necessary corrections and send it to the employer.