Where I've had success finding quality sales and BDC agents (that tend to strive toward and achieve management positions in their departments)...
1) Military - typically very disciplined and willing to listen to and follow process to the letter.
2) College grad with journalism/theatre background (Great for creative writing, responding competently, and, as it comes with a theatre background, great with scripts, inflection, tone, and body language).
3) Event management companies - great at preparation and thinking about the client experience.
4) Hospitality (specifically, at upscale resorts - great with customer service)
5) High-end retail outlets (think Nordstroms) where face-to-face interaction with customers and making suggestions is necessary, rather than someone at Kohls who just stocks racks or is a cashier
5) Bartenders and waitstaff, one where they serve a variety of customers, and not just regulars.