From the start position, your shoulders should be on top of the bar or slightly over with the ball over the ball of your foot.
Start your pull by pushing through your whole foot, while keeping your chest up.
In position 2, shins will vertical and shoulders will be over the bar.
As you move into position three, stay over the bar and don't pull back early.
You'll end in position three (the power position. You will have a slight bend in your knees, shoulders will be over the bar, and the bar will back in your hips.