Most people hang jumpers like they would hang a shirt or jacket, but the weight of the material means the hanger can create bumps on the garment's shoulders. Fortunately, there's a way to avoid this problem.
Joshua Davis shared his method for hanging sweaters on Snapguide, and it's a doozy. It will be easier to see what's going on by clicking the source link to see all of the photos, but he basically tells you to fold the sweater in half, place the hanger hook in the armpit, then fold each side of the garment over the hanger arms. The finished product looks a little strange, but it distributes the weight of the sweater more evenly over the hanger and eliminates those pesky bumps.
How to Hang a Sweater [Snapguide]