To know if you are parked within the lines and not obstructing other vehicles, check the position of your car before exiting it. Ensure that you are centered in the spot and not over the lines or too close to other vehicles. Use your mirrors and backup camera to help guide you into the spot, and take your time to ensure that you are parked safely and correctly. Avoid parking too close to other vehicles or obstructing their ability to enter or exit the spot, as this can cause frustration and potential damage to both vehicles.