Students have come to me to ask for letters of recommendation from time to time. As I have thought about it, it occurs to me to take a lesson from one of my mentors, Prof. Chris Healy at the University of Louisiana at Lafayette, whose policy on such matters is noted here.
To summarize, borrowing freely from my long-time academic advisor:
Students desiring to get a letter of recommendation from me should have made a B+ or better (or an HPR in remedial courses at TCI) in all coursework taken with me. That is to say, students need to have earned at least 87% of the total available grade for the course. Additionally, students seeking letters from me need to have been pleasantly memorable. Students should also submit an annotated curriculum vita or resume to me (an example appears here), as well as a writing sample (whether directly or via link to an online source), so that I can more specifically discuss their qualifications. Further, all information, forms, and materials that need to be turned in with the letter need to be given to me, as I cannot complete them if I do not have them.
Additional information typically helps, as well. The more I have, the more targeted and stronger a letter I can write.
Also, by requesting letters of recommendation, students necessarily give me permission to discuss their class performance with the recipients of the letters. I can hardly commend people without citing specifics, after all.
Please note also that I am happy to post letters to Interfolio or to other online platforms as need requires.