The student is authorized only to accept positions that are directly related to the student's major area of study. Beyond that there is little guidance and students are generally given a fair amount of leeway here.
What is the procedure for applying for OPT?
An F-1 student must request OPT from the DSO at his or her institution. The request must include a completed Form I-538 accompanied by the student's current Form I-20. If the DSO wishes to recommend the student be granted OPT and the DSO believes the proposed employment is directly related to the student's major area of study and commensurate with the student's educational level, the DSO will recommend OPT in SEVIS and print out the I-20 with the SEVIS recommendation.
More F-1 OPT ...