Third, word of mouth shows how the speaker fits into a community. Sernovitz used the Maker's Mark bourbon Ambassador Program as an example. Half a million consumers have signed up as ambassadors, which involve taking an oath to help prevent friends and family members from drinking cheap whiskey.

To generate the conversation, Maker's Mark doesn't advertise to ambassadors, Sernovitz said. Instead, the bourbon maker emails recipe ideas, updates on the latest batch of bourbon, and even sends high-visibility gifts a few times a year. “They give them reasons to keep talking about Maker's Mark all year long,” Sernovitz said.

One litmus test credit unions can use to see if their word of mouth advertising topic would work is to post it on the wall, he said, and ask if anybody in the room would be excited enough to tell a friend about it.

“If they can't answer a strong yes, you'll have to spend money advertising it,” he said.

One question from the audience following the prepared materials asked how credit unions can create word of mouth excitement from products and services that have been commoditized.

Sernovitz admitted that was a tall order, but said credit unions have two fundamental advantages over banks: a different relationship with members, and superior customer service. He used Commerce Bank as an example of how to generate buzz in a commoditized industry. When the bank moved into the Manhattan market, it differentiated itself by providing coin counting machines right inside the front door in an era when competitors were refusing to accept coins.

“That created a conversation,” he said.

Sernovitz is the author of the book, “Word of Mouth Marketing: How Smart Companies Get People Talking.” He is also CEO of SocialMedia.org in Austin, Texas, and runs the website WordofMouth.org, which provides free ideas for word of mouth marketing.