Provide specific details about the student.
General, abstract praise -- e.g. that someone has great analytical skills or writes beautifully -- simply won't help in such high-caliber competitions. Such general statements ought to be illustrated with specific examples -- e.g. a description of a specific paper that demonstrates those writing and analytical skills -- in order to show what makes the student in question special in your eyes. Someone reading your letter should easily see how and why you hold the applicant high in your esteem.
Where possible, referees can and should also speak to the candidate’s character and their ability to lead and use their talents to the full.
Give context to the applicant's relationship with you.
Show that you know the applicant personally. Provide some context of how you know the applicant — class, research, work, civic engagement, or other endeavor — and for what period of time. Discuss incidents or actions that you have personally supervised or witnessed, instead of rehashing other information that is on the resume but that you were not involved in. Point to specific examples of what the applicant has done. For example, if the student wrote a brilliant paper, mention its topic and why it stood out. If the student did outstanding work in another regard, explain the nature of this work and its particular strengths, especially as they relate to the goals of the fellowship.
Familiarize yourself with what they're applying for.
Fellowship-granting foundations have particular goals and selection criteria, which you should speak to in your letter in order to emphasize the fit between the applicant's strengths and what the selection committee is looking for. Even entirely positive letters may not be helpful if they do not speak to the award at hand. ONFS is here to help if/when you are asked for a letter for a fellowship that's new to you, so please don't hesitate to ask us.
Place the applicant in a larger context.
Situate the student in the context of your academic discipline when they are proposing to do graduate study or research in the field. If they are admissible to top doctoral programs, for example, say so. If you've trained them in historical methods and are thus confident that they will make the most of a year in the archives, for example, say so.
Beyond the disciplinary context, a strong letter might compare the present applicant to other students you've taught -- e.g. s/he is one of the best students I've had in my 13-year career -- or to others who have applied for, and perhaps won, similar honors in the past.
Letters that are too short and that fail to provide specific examples or instances of points mentioned do not help the candidate.
Generic letters, or letters written for another purpose and sent without regard to the specific fellowship, course of study, or project proposed may hurt the applicant more than help.
Further, good letters should help the applicant stand out among their peers, not merely summarize information available elsewhere in the application or only present the student’s grade or rank in class. Be specific, never generic.
Letters that focus too much on the context of how the writer knows the applicant (descriptions of the course or its approaches) and not sufficiently on the student and his or her accomplishments would detract. The student is applying — not the recommender.
Letters should not consist largely of unsupported praise. Kind words that do not give committees a strong sense of how applicants have distinguished themselves are not helpful. Provide examples to show praise is genuine.
It is not helpful to say that a student did what might be expected (e.g. attended class, completed all the reading assignments) or that point to qualities (e.g. punctuality) not germane to the fellowship. If these are the only positive things you're able to say, then you may not be well suited to write this letter. What will help in the letter is that you explain what makes the student an exceptional candidate for this opportunity in particular.
Veiled or indirect criticism
Letters that may be read as implying criticism (beware of left-handed compliments), or whose criticisms might be taken to indicate stronger reservations than stated, are not helpful to the student. Letters should be frank and honest — and honest criticism, if generously presented, can enhance the force of a letter — but committees take critical comments very seriously. It is best to be cautious when making critical remarks and to avoid any sense of indirection.