I believe retailers need to imbue their organizations with a culture of training. It should start the moment an employee walks through the door and continue forever. First document your systems and then train your systems, policies and procedures. Assign mentors to your new people, and reward the mentor for the success of the new person. Yes, this is a lot of work, but it's worth it.
Nothing is as discouraging as chaos and confusion.
That's why cross-training is so important. Some stores spend about a week each year swapping jobs, with the salespeople riding the delivery trucks and the warehouse workers visiting the sales floor. This can create valuable empathy between departments while also helping everybody understand some of the challenges their colleagues face. I also recommend tuition support for employees pursuing adult education, even when the classes seem to have little to do with retailing or business. If it's important enough to one of your employees that he or she wants to attend classes after hours, then it should be important enough to you, too.