Final answer:
Before changing lanes, you should glance over your shoulder into the lane you want to enter to check your blind spot after looking into your outside mirror.
Step-by-step explanation:
Before you change lanes, you should glance over your shoulder into the lane you want to enter. This practice is often referred to as checking your 'blind spot', which is the area that may not be visible in your mirrors. It is essential for safe driving to both look into your outside mirror and glance over your shoulder. The act of turning your head to check your blind spot ensures that there are no other vehicles or obstacles in the space you are planning to move into. It's important to note that you should check over either shoulder depending on the direction of the lane change; for a right lane change, look over your right shoulder, and for a left lane change, look over your left shoulder.