Ken, we supplemented existing shelving in one of the closets in our old home with Rubbermaid hardware similar to this
The system is well-designed and very strong. You install a horizontal rail at the top -- ideally into studs -- which gives you a level starting point. You then hang the vertical rails from it at your required width -- again, ideally in front of studs -- and then screw those into place. Use three tails if you're spanning a large width. Then you pop shelf brackets onto the rails at your desired heights and throw your wood shelves onto them. Highly recommended.
You'll need to return some of that lumber, though.