Here’s a quick, three-paragraph template for writing a letter of recommendation. Don’t overthink it; these should be quick to read, and leave a strong positive feeling on behalf of the candidate.
Paragraph 1: What are you doing, and why?
The opening is a simple statement of what you are doing: “I am recommending [candidate] for [promotion/acceptance] to [level/program].” This is then followed by your reasoning; choose one or two qualities that represent the program they are applying for, and give an example about how they express this quality.
You don’t need to go into explicit detail; remember that this letter is part of a larger application, and your goal is simply to add weight to the overall packet.
Paragraph 2: How does the organization benefit?
Next, detail one or two clear benefits to the program for accepting this candidate. Unambiguously tie success directly to this applicant; the goal is to create organizational incentive for accepting the candidate.
Be direct; unambiguously answer the question: “What do we gain if we accept this candidate”, and make it something valuable.
Paragraph 3: How does the candidate benefit?
The last paragraph should be about the candidate, and how / why they will benefit from being accepted. Explain how they are motivated and engaged for personal reasons, and will be an active participant in the program. Nobody likes a freeloader.
Done? Share it with the candidate!
Unless there are real reasons to keep your identity private from the candidate, share your recommendation with them. Everyone enjoys recognition, and it will only serve to strengthen your relationship with them in the long run.