Step 1: Motivation
I already had a few hand-built bookcases, like these, but I needed more space, and I wanted them attached to the wall.
Step 2: Cost and tools
I spent $100 at Home Depot getting 3 standards (the rails), 15 brackets, 5 10 in x 48 in shelves, and screws (I used 2 in and 1 1/4 in).
Stud finder (I prefer using a magnet)