Calculate the number of shelves for the project and their approximate location on the garage walls. Check the walls to see if there will be any additional support needed for the shelving. If the wall is cinder block or brick, you must affix studs with concrete screws.
Decide how long the shelves will be and how many shelves you'll hang. Measure the length with a measuring tape and note the length. Also, measure out from the wall to determine the width of the piece of wood.
Take the shelf dimensions to a lumberyard or home improvement store, like Lowe's or Home Depot, and select the lumber for the project and have each shelf cut to size.
Purchase a shelf bracket kit while at the home improvement center. Buy as many of these kits needed for each shelf with at least two brackets per shelf. These kits may include a track system that requires screwing them into the studs.
Hang each wood shelf piece in place on the shelf brackets and affix with supplied hardware or simply screw into place.
Continue hanging shelving until the desired number of shelves are in place.