Before you begin the process to install shingles, first determine what type of shingling job you will be doing. If you will be replacing a few shingles, the process will be different than the process for replacing all the shingles on the roof. Also determine what type of shingles you need, and how many shingles you will need to cover the entire roof. When purchasing shingles, be sure to purchase extras that can be used for replacing damaged shingles later on down the road. You will need plenty of nails to install shingles properly, so be sure to buy all the materials you will need before getting started.
Keep in mind that you should take every safety precaution you can when you intend to install shingles. This includes using sturdy ladders that are tall enough and in good working order, wearing non-slip shoes that will allow you to gain traction on sloped roofs, and securing tools properly so they do not slide off the roof. Do not attempt to install shingles in cold and icy conditions, or at night without proper lighting. It is always best to work with a partner, or at least let someone know that you will be working on the roof.
Once you have determined the proper amount of shingles you will need for your project, you should determine whether you need to remove the old roofing materials first. In some cases, it is acceptable to install new shingles over old ones, but it is usually best to replace all shingles if possible. Before you install shingles over old ones, be sure to hammer down any protruding nails that may have worked loose over the years. Replace damaged shingles only, and make sure the surrounding shingles are secure as well.
Before you install shingles on a new roof, be sure that the materials underneath the shingles are properly installed. Roofing felt should be installed over any plywood before nailing shingles in place. Once the felt is secured, draw a chalk line in the center of the roof and start shingling there. The first shingles should be secured at the eaves, or lowest part of the roof. These shingles will overhang the eaves slightly and be secured later. Measure for the next row of shingles by snapping a chalk line above the first course of shingles. The chalk line should be about five inches (12.7 cm) above the first course of shingles. Do this for each successive row of shingles. Continue all the way up to the peak of the roof, and consult manufacturer's specifications for shingling the peak as well as any valleys in the roof.