Walk around the perimeter of your home to trample down some of the snow. Having a path will make it easier when you're using the roof rake and will prevent your feet and legs from getting stuck in snow while you're working, especially if there are high drifts.
Follow the roof rake manufacturer's instructions and assemble the roof rake along with the pole extension. Roof rakes come in a variety of sizes and are commonly sold in 16- and 21-foot lengths. However, for a two-story home, you'll also need a pole extension that installs directly into the end of rake and gives you greater reach.
Raise the roof rake up to a corner of the roof and place it 3 to 4 feet up from the base of the roof. Pull back on the handle, which will bring the snow with it. Instead of scraping the shingles clean, leave a very thin layer of snow on the roof because scraping the shingles can damage them and lead to roof leaks.
Work your way from one side of the roof to the other until a row of snow has been cleared around the entire roof. Don't worry about raking the entire roof, but instead focus on the areas that are easy to access. That alone will be enough to relieve pressure off the roof and prevent a collapse.