Position the barbell on your neck/shoulders. Take an overhand grip of the bar. With your toes pointing out and feet shoulder width apart, bring your torso forward and down. Move your hips back to keep balance. Inhale on the way down. Exhale on the way up.
Think of the good morning exercise as a half squat. Your form and preparation for the exercises is identical except that in performing the Good Morning exercise you don't actually squat.
To do this exercise you will first need to position the barbell on your shoulders. There are two ways to hold the barbell. You could either hold it above your shoulders on your trapezius or a little lower, on your rear shoulders. Note that since you'll be leaning forward, the lower along your back you place the weight the easier it will be to perform the exercise. You should place the bar where it's most comfortable for you. Also, don't forget to consider how you grip the bar. You could either have an overhand grip with your thumb on the same side as your fingers, or your thumb opposing your fingers. If you are just starting out we recommend that you take a full grip of the bar, with your thumb opposing your fingers. This will help you balance the weight and prevent it from slipping out. Generally though, especially as you go heavier, the thumb should go onto the same side as your fingers. This will help you keep your wrist and forearms straight, eliminating unneccessary strain.