Purchase a snow rake, which is a long handle with a solid piece of metal on the end at a 90-degree angle. Some snow rakes have a solid handle, while others can be extended. Be sure the rake you choose is long enough to reach your roof.
Stand beneath your roof. Extend the rake's handle so you can reach the center of your roof. Place the flat part of the rake in the snow and pull it toward you to drag the snow off the shingles. Don't rake all the snow off; the rake may damage the shingles. Leave a couple of inches of snow to serve as a protective layer.
Repeat the process on the rest of the roof, removing snow where it is deepest and working your way to more shallow areas.