Keep your writing action-oriented. Begin each paragraph with a punchy, active affirmation of the candidate’s qualities or character. Strong verbs are your friend.
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.