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.
Why should I use the Letter Service at the Career Center? If you are applying to more than three schools, or you think you want your letters held for other opportunities (like law school) in the future, you should plan to use the Letter Service. Your letter writers will write one letter and fill out one form, rather than filling out a different form for every application.