Drive ahead until you are approximately three stalls ahead of the one you want to back into. Your right or left-view mirror should be positioned slightly behind the last line of the third stall, depending on whether the stalls are to your right or left. Look over your shoulder and make certain the first line of the stall you are aiming for is visible from your backside window.
Take your foot partially off the breaks and immediately begin turning your steering wheel toward the stall. Turn too early and you will undershoot the stall, and turn too late and you will overshoot it. The key is to move your car slowly while turning fast.
Hold your steering wheel tightly to the left or right until your vehicle is parallel to the stall. Let go of your steering wheel too early or hold on too long after turning parallel and you will cause your car to come too close to one of the stall's sides. The goal is to line it in the center of the stall.
Stop your car and make certain that you are neither too right or too left. Make a slight adjustment to the left or right with your steering wheel if your car is indeed too tilted to one side. Let go of the breaks and continue backing into the stall. Carefully watch through the back-side window to make sure you do not bump into the parking stop.