We cut the supports 16 in. long, but you can place the second shelf at whatever height you like. Screw the end supports to the walls at each end. Use drywall anchors if you can’t hit a stud. Then mark the position of the middle supports onto the top and bottom shelves with a square and drill 5/32-in. clearance holes through the shelves. Drive 1-5/8-in. screws through the shelf into the supports. You can apply this same concept to garage storage. See how to build double-decker garage storage shelves here.
The key to making furniture is having a plan. (Or is that the key to life? I always forget.) The good news for beginning woodworkers is that you don’t need to develop the plan; you need only to follow it. Project plans are abundant and easily found (check out Chapter 21 for some project-plan resources). After you get familiar with the way plans are written, you can build just about anything (depending on your skills, of course).