I worked in a large new and used family-owned bookstore for more than 10 years, starting in high school. During my time there we learned how to deal with crazy people and belligerent transients, and developed procedures for dealing with shoplifters that helped us reduce shrinkage and keep staff and customers safe. We did this organically over a period of years, primarily as a collaboration between myself and one of the store owners.
I learned a lot about loss prevention, handling difficult---and sometimes dangerous---people, and how you can make your store procedures and guidelines safer and more effective. This post contains a variety of observations I've gathered from my experiences.