Advisory Circular 65-30B with Change 1, Overview of the Aviation Maintenance Profession
This advisory circular (AC) was prepared by the Federal Aviation Administration (FAA) Flight Standards Service (FS) to provide information to prospective Airframe and Powerplant (A&P) mechanics and other aviation maintenance professionals interested in a career in aviation maintenance. It contains general information about the requirements to become a certificated or noncertificated aviation maintenance professional.
Download -Advisory Circular 65-30B, with Change 1

Additional information from the FAA:

• FAA Airman Knowledge Testing Authorization Requirements Matrix
• Form FAA 8610-2 - Airman Certificate and/or Rating Application – Mechanic and Parachute Rigger