The key is keeping your back straight, so try this: get the bar in position, bend over and grab it overhanded, and then adjust your stance so your hips and legs are comfortable and supporting your torso. I find on these a bit wider than shoulder width stance for my feet works best. Also, do not look up. It seems almost a natural tendency, but you will have an easier time of keeping your back straight if you keep your neck straight on this one. Look at the floor, keep looking at the floor. When people break form on this exercise it's almost always when they look up.