I believe I've procured 4 professors/advisers to write recommendation letters for me for my grad school applications. It just so happens that 3 are active in my research area of interest, but I have a really strong friendship with 4th one as I've known him the longest (freshman physics professor/tutor) and has seen my progress much more closely (we often see each other many times a year and always have interesting discussions about physics). Since some schools ask for 3 rec letters tops, I would much prefer his words over some of the other profs since he would probably describe me a lot better. The problem is that he doesn't have much/any experience writing recommendation letters compared to the other profs, so he's asking me what kind of things I would like him to mention in his letters. He is an adjunct prof at his alma matter, where I studied before transferring to another uni, so I am thinking he should mention how harsh the university grades and how I compare to other students, are there any other important things that should be mentioned?