For proper posture when standing, follow these tips:
Always maintain the three natural curves of your back.
Visualize an imaginary string running through your body; stand so that your ears, shoulders and hips are in a straight line.
Stand close to your work so you don't have to slouch over it.
Bend your knees slightly when you stand, and distribute your weight evenly on both feet.
Rest one foot on a low ledge, step or rail when standing for an extended time; switch feet every few minutes.
Wear comfortable, low-heeled shoes and stand on a floor mat.