Here is a good story from IBD about Helzberg, before he sold out to Warren Buffett. There are some very good strategy tidbits in the article, like:
The highest-performing stores with the best managers were the best place to test new ideas. "That was really totally counterintuitive for me," Helzberg said. "At first I thought you should test in an average store. But when you test in your best store, you are not just testing. You set a standard. You prove it can be done. It was like Roger Banister breaking the four-minute mile. Before he did, they said it couldn't be done. But one man does it, and the next year 29 others do it."