Create a shelving frame with sturdy two-by-four boards, metal or plastic. The lumber boards make the most cost-effective frame. Measure the building materials, and cut them to create frame posts. Pre-drill the posts to avoid splintering. Place two pairs of posts, and drill several support beams between them. These become the shelf's end pieces. Secure pairs of top, bottom and center shelf supports between the end pieces. Top these supports with plywood sheets to create the shelf.
Drill the shelves together with galvanized screws for the most secure fitting, but drywall screws are a cheaper yet still effective option. After assembling the end pieces, which should resemble a ladder, check the levels to make sure the posts and support beams are even. Attach end brackets to the end pieces that later secure the plywood shelves in place.
The length of the shelf supports dictates the width of the storage shelves. The number of shelf supports dictates the number of shelves. When the screws have been sufficiently drilled into the structure and it is stable, stand the storage shelf up so the end pieces are at either end with the frame posts running perpendicular to the floor. Cut the plywood boards so the length is equal to the length of the shelf supports, and the width is equal to the distance between the frame posts. Trim excess wood off the plywood boards to fit onto the shelf supports and into the end brackets.