The distance between you and the steering wheel is also important. Mutchler said, "When you put your arm straight out, your wrist should rest on top of the rim." And if you were taught "10 and 2 o'clock" on the steering wheel, it's actually more like "9 and 3 o'clock."
If you have an adjustable seatbelt anchor, position the seatbelt high enough that it doesn't easily slide off your shoulder. Having the seat positioned properly will help the belts hold you securely in case of an accident. Minor tweaks like these can make a major difference on the road.
Another tip: you want to position your right foot so you can pivot from the accelerator to the brake pedal without taking your heel off the floor of the car. That way, you're equally prepared to avoid an accident whether you need to speed up or stop short.
Another reason to find a comfortable driving position: fidgeting in the seat leads to constant speed changes and decreases fuel economy.