Final answer:
Before adjusting seats, seatbelts, or mirrors, confirm the vehicle is in park or neutral to prevent unintentional movement.
Step-by-step explanation:
The first step to prepare to drive a vehicle safely should be to ensure the vehicle is in park or neutral. This is a fundamental safety precaution to prevent unintentional vehicle movement when starting the car or adjusting your position in the driver's seat. After confirming the vehicle's gear position, you should then proceed with the other safety preparations such as adjusting the seat, seatbelt, mirrors, clearing the view, and locking the doors in that order.