Count the number of DVDs you currently have and add in any number you plan to have in the future. Each DVD storage case represents 1/2 inch of shelf space you'll need, so if you have 200 DVDs you will need 100 inches of total shelf space.
Divide the number/amount of needed storage space by the number of racks you want. This will give you the amount of storage space for each rack. For example, if you want 5 shelves to store your 200 DVDS, each shelf will be 100 inches/5 shelves = 20 inches per shelf.
Cut pieces of 1-by-6 or 1-by-7-inch lumber with a saw. You need pieces for each DVD shelf you plan to have plus one. The pieces should be one to two inches longer than your above-measured shelf length.
Construct the support walls for your racks: Cut pieces of the same lumber that are 8 inches long, or cut 1/2 to 1-inch thick dowel sticks into 10-inch long pieces.
Drill holes into the corners of your shelf pieces if you are using the dowel sticks; use a drill with a bit the same size as your dowel thickness.
Fasten the supports to the ends of one shelf piece using wood glue. If you are using the dowel sticks, apply the glue near the ends of the rods and insert them in the drilled holes.
Glue another shelf board on top of the support pieces to complete one rack shelf. Repeat the previous steps for gluing supports and an upper shelf to complete your total number of shelves.