How to write a letter for a student
Your former student asked you to write a reference letter. How do you do that? This is a practical guide. Basic steps:
Write a letter
Check that your letter is accurate, non-sexist, and positive
Make PDF and submit.
You need to know a lot of information before you can write someone a reference letter. Some of it is practical: where to send the letter? when? to whom? Some of it is about the job: title, location, etc. This information is required to write any letter and your candidate should be able to send it to you quickly.
To write a good letter, though, you'll need more information. Why does the candidate want this job? Why would they be good at it? You need to know about their technical qualifications, their character, their ability to work in groups, their writing skill. How does the job fit into their life goals? Most students are applying for REUs or graduate school, so you should assess their research readiness.
Luckily, your student can send you all this information. Sometimes they don't really know, so this is an opportunity for you to help them clarify their goals. Sometimes their goals are specific to a kind of position, but not a particular position. That's ok. Encourage them to be reflective, but they don't need to manufacture reasons. Because the academic job market (even for REU positions) is incredibly competitive, you don't want your student to fall in love with only one position at a time.
To write a great letter, you need to contextualize all this information with specific evidence and comparison groups: your student is not just a great writer, she is the first author on a paper you published. He's not just good at physics, he earned the highest grade in your upper-division course and other students regularly turn to him for support. She's not just a leader, she was president of the SPS chapter and organized a student movement to connect community needs and university resources. He's not just a good teacher, he was among 3 students selected from a pool of 50 to tutor in your introductory class.
You can gather some of this evidence from the student by asking for specifics, but for other parts you'll need to look into your own records or search for specific anecdotes. Some people require that students fill out the answers to questions ahead of time; other people want to meet with each student. The details of how to gather this information are up to you.
Write a letter
Your letter needs to be on letterhead, which you should acquire (or recreate) from your institution. It's not enough to print it on letterhead paper; you need letterhead PDF. If your institution is cagey about giving you a template, don't despair. Pretty much nobody knows what your official template looks like and you can probably (re)create it pretty well.
Your letter should follow this template, though you can personalize the exact language.
This letter is a recommendation for $Student and $Position.
My position is ...
I have known $Student in $Capacity for $Duration.
Short, comparative evaluation of $Student with clearly identified comparison group ("top 5% of over 100 upper-division students over 10 years" / "top 3 of over 60 undergraduate research students" / etc)
$Student is good for your position because of specific research/teaching/classroom experience. Tell a story and contextualize it.
$Student has the following human qualities which are great for this position.
OR: $Student's record does not accurately reflect their capabilities because of $reasons.
$Student is super awesome (or other accurate language)
Please contact me over email / the phone (preferred contact info). I would love to discuss $Student further!
Shoot for about 1-2 pages, and be specific without being wordy.
Check for sexism in your letter.
Is your letter full of sexist language which will unfairly bias employers or admissions committees against your student? Women are praided for being hardworking; men are praised for brilliance. It turns out that being hardworking is a better predictor of success than brilliance. Physicists are more likely to hire people described as brilliant, thus perpetuating the sexist cycle of assholery in physics, materially harming prospective physicists, and degrading the quality of research in the field.
There's loads of other sexist language which creeps into reference letters. Here's some references for you to check and an online calculator. They're not perfect, especially for education researchers who need to use the words "students" and "education" a lot, but you should use them anyways.
Fix your sexist language. For students of all genders, balance weaker / feminine words with stronger / masculine words. Especially pay attention to this problem for female students, as you cannot depend on your co-letter-writers to be fair.
Once you've fixed your sexist language -- possibly by inserting some more strong adjectives and verbs -- make sure that your letter is accurate and contains precise comparisons with explicit comparison groups.
PDF and send!
Here is a dirty secret: a lot of places do not want your letter. They want you to fill out a form with clicky boxes and perhaps also specific text prompts. This makes their lives easier to compare many applicants, but wastes your time because nobody has the same forms. This is a stupid move on their part, because pissing off recommenders only serves to harm applicants, but hey: they've got the power and you do not. The vast majority of these forms accept a letter in addition to their clicky boxes, which you should upload but not assume they're actually reading.
That said, if your student is applying to a normal number of jobs or fellowships, one of them will probably want a letter. Make sure you PDF it and send it to the right place.
Is it ok to say no to a student?
Yes, of course! Here are some common reasons:
Student didn't give you enough time to write a letter. It takes time to craft a good letter. Beyond simply writing, there's time to gather information about the student and the position, think about how you're going to frame the student for the position, build a good comparison set, etc. If you already have a letter for that student for a similar job, you might be able to write a new letter quickly. But if not, it's ok to say no.
You don't like the student. Writing letters is a professional favor. No is a complete sentence.
You don't think student would be good at the job. Be honest with yourself: is this because you think the job is a bad match (in which case you should counsel the student against applying), or is this because you think the student doesn't have the qualifications to do the job well (in which case you might recuse yourself)?
You don't know enough about student to make a detailed recommendation. This is often a cover for one of the two above reasons, and it's easily solved by a bunch of detailed questions.
The job needs some very specific kinds of recommenders, and you're the wrong kind. If the job needs someone who has observed student teaching and you haven't, then a letter from you might be harmful. Similarly, if student is getting three letters from classroom teachers for a research position, the lack of breadth is a red flag.
I want to write a letter for this student and their record doesn't reflect their abilities.
It's possible that your student has had some hardships to overcome, and those struggles make their application look less appealing on the surface. Maybe their GPA is low because they also work full-time, or maybe they've taken some courses out of order because they are a transfer student.
You should discuss with your student how they'd like you to address these issues. It's perfectly normal and often a good thing to talk about them in a reference letter, but be careful: don't disclose something your student doesn't want their new program to know about.
Your student has strengths (possibly non-traditional ones) that you can highlight even if you don't reveal reasons for why traditional measures of academic worth don't appropriately capture their abilities. You can also carefully massage comparison groups to show your student in the best possible light.
I want to write a letter for this student, but I think they wouldn't be good at the position.
Before you torpedo them,
Examine your own implicit biases to make sure you're not being a sexist or racist asshole.
Examine why you want to write a letter. It's ok to decline to write a letter.
What can/should you legally and ethically disclose about why you think they wouldn't be good at it?
If you still want to write the letter,
Seek balancing information: maybe you think they'd do well with a particular kind of mentoring, or they'd be good at some aspects of the job and not others. It's ok to highlight the good parts and nod quietly to the areas for growth.
Write a succinct summary of the letter and run it by another colleague for advice. Run it by the student to see if they still want you to write the letter.
Be aware that all recommendation letters from the US are ridiculously overblown and the market is very competitive. A lukewarm letter is really a kiss of death.
Hey, can I use this as a guide for writing tenure letters?
No. Tenure letters are not overblown the way recommendation letters are. It's a different genre. You should still minimize sexist language, check for accuracy, articulate appropriate comparison groups, and use letterhead. However, your sources of information, template for letter writing, and audience are totally different.