Back in 2009, Ryan Beal, an independent financial advisor with Ameriprise Financial Services in Dublin, Ohio, began working in nearby Columbus at the CME Credit Union, which had started out 75 years earlier as a credit union for police and firefighters.

Although it had long since opened its doors to the whole community, it still had some legacy members who were active or retired uniformed employees.

Beal says he discovered that those employees, both cops and firefighters, had a tight community among their colleagues and that because “we got along well” and because he did well by them, his police and firefighter clients were quick to recommend him to co-workers.

By 2013, he had so many police and firefighter accounts that he decided to focus on them entirely, and so he shifted almost 70% of his client book over to other advisors. Later, Beal went independent as Flashpoint Asset Strategies, bringing most of that uniformed clientele with him.

With $20 million in assets under management today, he says he has discovered that tapping into professions such as police or firefighters can be a perfect way to gain referrals and build a business.

“A niche market is a great way to go,” Beal says. “If you do well, everyone in the group will hear about it, but the corollary is that if you mess up, everyone will hear about that, too.”

Beal says cops and firefighters are somewhat unique because they are so close-knit, but he suggests that the same approach could work with professions such as lawyers or physicians, though the approach might have to be different.

“It’s important in approaching any group you offer to help, nobody likes being sold something,” he says.

“I always open group meetings on their turf, and I ask them what they want to talk about,” Beal says.

“They set the agenda. Then if anyone wants to talk with me about their account, I’ll set up an appointment with them later,” Beal says.

“Certain groups think they know everything, and they want to be validated. That would be like docs and lawyers,” Beal says.

“For others, like my clients, investing is so far from anything they know about, they want to be educated,” he says.

Rick Rummage, principal of The Rummage Group, an advisor training firm in Herndon, Va., says,

“Anytime you can get clients who are in a profession, like physicians in a community, it’s great for referrals [doctors are particularly good at referring people to a good advisor]. But it really helps when you’re looking for that niche, if you’ve got a passion for it or have some connection.”

In Beal’s case, he says there are no cops or firefighters in his family, and he isn’t a volunteer firefighter himself, but he says, “My personality just seems to click with these people. We really hit it off.”

Dave Lindorff spent five years as a China correspondent for Businessweek and has written for The Nation and Salon.com.

This story is part of a 30-day series on how to generate the best referrals.