Target the recommendation. Is it for an academic post, a job, a volunteer position, a background check, or a personal reference? Write your letter so that it is focused on this purpose. For example, if the letter is part of a job application package, it should focus on the professional qualifications and conduct of the candidate.
Writing a letter of recommendation can be intimidating, especially because the person you’re writing it for is counting on you to pull through for them. Fortunately, there’s a general formula you can use to write a letter of recommendation that is both professional and effective.