Design a square with side measurements equal to the width of the shelving you will install. A corner, in general, meets at a 90-degree angle, so your square must be absolutely square.
Cut one square from one of the plywood shelves. Test the square in the corner to make sure the two pieces of plywood shelves that meet from each side at the other right angle fit. Whether you are using 12-inch or 24-inch-deep boards, each angle edge must be the same measurement.
Piece together a corner with one shelf and screw in a steel brace over where the two edges meet. Add on the other shelf the same way. Once you have installed wall brackets, utilizing wall studs along the way, place the complete shelving unit onto the wall brackets. If you are doing a large expanse of shelving, have a friend help you with lifting the shelves into place to avoid straining any shelving connections.
Complete all the shelving units the same way. Once they are all in place, add more security in the corner by screwing in two small 1-inch-by-1-inch wood strips just underneath the corner wall angles where they meet. Screw through from the top of the corner section into the wood strips underneath.