The M-Course Form details the course requirements for Writing in the Major [M] status. It will need to be filled out completely and submitted in order for your course to be considered for [M] status.
An M-Course can be two or three credits. Two-credit courses must have at least 60% of the course grade based on writing assignments, and three-credit courses must have at least 30% of the course grade based on writing assignments.
Yes; because M-Courses are designed around writing in the major, and major-specific writing begins at the 300 level, M-Courses must be 300 level or above.