In good posture, your back is fairly straight, but not stiff. Feel tall. Your arms should hang loosely from your shoulder joints and you should feel your weight distributed evenly between your heels and the balls of your feet. Your knees should feel alive - I like to use the word “springy”. This posture allows you to use your big muscles, turn your body around your spine, use the ground for leverage and take advantage of centrifugal force to accelerate the club.