What is the proper procedure for teaching a student to back up safely?

1. Only use the backup camera and ignore mirrors when reversing
2. Turn the body to look through the rear window, use mirrors as supplementary reference, and back up slowly
3. Use only the side mirrors while keeping the body facing forward in the seat — backing safely means looking through the rear window while moving slowly.
4. Have a passenger outside the vehicle guide the driver verbally at all times