Before you acquire materials you must calculate the surface area of your roof. You cannot simply measure the length and width of your house and multiply them together. You must take into account the pitch of your roof as well as any added gables or dormers. This means that you should draw a map of your roof, then climbing up there and take measurements of the various surfaces. Make use of your high-school math and recall that Length X Width = Area. For triangular areas it is Length X Height X 1/2 = Area. Add up all your surface areas and you should come up with a close approximation of square footage.
Asphalt shingles come in bundles. Normally 3 or 4 bundles make up a square. A square of shingles is the number of shingles covers 100 square feet of roofing area. A bundle of shingles weighs about 70 pounds. The weight is just manageable for a good sized man. There are about 27 strips to the bundle. Once at the job site, these bundles can be opened and the shingles handled in smaller quantities. For transporting these items to a roof, professionals use conveyor belts or fork lifts. In my younger days I would sling a whole bundle over my shoulder and heft it up the extension ladder, but now, for small jobs, I generally take half a bundle at a time. Better to make twice the trips up and down the ladder than drop a bundle on someone's head or fall from a ladder because the weight is too unwieldy.
You will notice with three tab shingles that there are spaces between each tab. This is primarily for looks - a solid run of asphalt shingle would work just as well. On the top side, in about the middle of the shingle, you will find a strip of plastic covering an adhesive. The plastic protects the shingles while they are stacked. For the best seal on the roof the plastic strips should be removed as the shingles are placed.
A layer of felt paper is put down before the shingles are hammered home. Felt paper comes in rolls and generally has painted lines that you can use as a guide for keeping shingles straight as they are laid. Rolls come in various lengths. Consult the packaging for the number of rolls you will need.
Roofing nails are fairly short and have a fair sized head. This makes them ideal for holding down the soft asphalt shingles. Be sure that your nails are long enough to penetrate through any layers of shingles as well as the plywood sheathing. (1 1/4 inch nails should be sufficient for a new roof. Use 1 1/2 if going over a layer of old shingles.) A large quantity will be necessary. Each shingle will take a minimum of four nails to secure it to the roof. With an average of 81 shingles in a square, this means that you will need a minimum of 324 nails per 100 square feet. Be sure to factor in slop. There will undoubtedly be some lost nails, here and there, plus roof peaks, flashing and drip edge will all take their tithe of nails.
Drip-edge is used help protect the trim boards, facia boards and gable-ends. This is usually made of light aluminum sheet metal, easily cut by tin snips. It also helps prevent moisture coming back up underneath the shingles at the edge of the roof.
Flashing is basically a role of sheet metal. Flashing may be cut with tin snips. It is placed around vertical surfaces such as chimneys and dormers as well as in valleys in order to form an impermeable barrier at these vulnerable points. There is specially designed pipe-flashing with a rubber gasket that helps seal vent pipes that protrude through the roof.