$1 is by the organization I got all of my training from, years ago, and nothing's really changed since then. Basically, check prices online as much as possible so I know exactly what I want before I head out, go with a sighted friend every so often to make as many bulk purchases as possible in large stores like Costco, and do all the other shopping at smaller stores where it's possible to memorize the layout, and/or ask for help from the staff.