This is how I've gone about it in the past: I've asked the person to show me the description of the position he or she is applying for. Then, after mulling over the traits a person would have to succeed in the position, I jot down some notes about the person, focusing on specific situations in which those traits were exhibited. I mix a blend of general positive character traits with concrete examples of how those traits were used in specific instances. For example, "Jane brings a strong work ethic toward any task she undertakes. When our company underwent an internal audit, Jane, on her own initiative, came in on a Saturday, spending the day ordering her customer accounts." The first sentence is a general claim; the second backs it up with an example. . . Also, since you're vouching for this person's skills, etc, you're going to want to be sure your grammar, punctuation, and mechanics are correct. The letter you write is a reflection on the applicant, and you want to put your best voice forward as well. . . The most important element of a good letter is matching the traits of the person to the job's description in clear, concise language. Be sure your verbs are precise, the language is active, and your tone is confident and positive about the applicant's skills and attributes. . . Not only will the hiring committee read the letters, but they'll also focus on the resume, CV, and the applicant's own cover letter. So, you may even consider taking a look at the applicant's stuff. You want to add to the image of the person not merely repeat things that she's already written in her resume, CV, and cover letter. . . This is a crash course, but if you like what I'm saying, you can contact me via Answers, and I'll go into more detail.