Generally a letter will start out with the statement that the writer is pleased to write a letter of recommendation for
Your Name Here. Then it goes on to describe how long the writer has known the applicant and the nature of the relationship (supervisor, instructor, division chief, etc).
Next paragraph usually describes what your job has entailed. Have you been promoted? Obtained a leadership or training role? Done something special for morale?
Next paragraph usually describes the attributes that you've demonstrated on the job that will make you a good student or a good doctor.
The next paragraph is optional but this is the place to put any negatives followed, if possible, with something positive that shows that you've grown. (Although Jack had trouble early on ... he quickly learned to ... and gained the respect and the admiration of ....)
The summary paragraph usually says something about your rank among your peers (among the top 5% of ....), the writer's confidence to have you as his physician, some regret that you will not continue on with some other career (laboratory or firefighter, etc) and closes with a general recommendation (I am pleased to recommend (or highly recommend, or most highly recommend) Mr. Jones for admission to medical school). Some writers offer their phone number if the reader has any questions (I've never known anyone to call ... I've made one call -- only because the letter was confusing -- a bad job of cut & paste of a letter written for someone else
).
