Extend an extension ladder so that it is 3 feet above the edge of the roof. Lean the ladder against the roof at an access point that does not block any points of egress. Make sure that it stands on firm, flat ice-free ground.
Climb up the ladder and onto the roof. Have a partner hold the ladder steady.
Shovel the snow off of the roof with a plastic shovel. Start at the top of the roof (or center of a flat roof) and shovel outward toward the eaves to scoop all of the snow off onto the ground. Do not apply heavy pressure as you shovel. You may damage the shingles. Do not scrape the bottom layer of snow off of the shingles. You may disturb their waterproof coating.
Climb down the ladder. Have your partner hold the ladder as you climb down. Loosen the safety rope's slack as you climb.