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.
Some applications, such as professional schools give applicants the choice to waive their right to view their letters or not. Usually, applicants are encouraged to waive their rights because if they do not, it is a sign they are not confident in their recommenders.