The No. 1 phrase people who are good at small talk always use, says Stanford public speaking expert

Small talk might seem trivial, but it can deliver big results.

It can help us forge new or deeper connections with others by allowing us to discover unexpected areas of common interest. It can enable us to establish or reinforce our personal reputations, giving us an opportunity to demonstrate warmth and empathy.

I'm a Stanford lecturer, podcast host and communication expert, and I was always so inspired by my mother-in-law's manners and impressive interpersonal skills.

Her favorite phrase was "Tell me more," and it happens to be one that people who are good at small talk always use.

Most members of my immediate family weren't so great at taking turns and actively listening during conversations. We all spoke at once without listening to each other. Whoever spoke loudest and longest was heard. The others weren't.

Don't miss: Harvard psychologist: If you use any of these 9 phrases every day, 'you're more emotionally resilient than most'

So, imagine how striking it was to see my mother-in-law willingly cede the floor, giving permission to the other person to speak by saying, "Tell me more." It seemed like such a generous, empathic act.

I sensed immediately how much connection she forged with those three simple words, and I saw how much she learned from the people with whom she conversed.

"Tell me more" is a support response; it supports what the other person is saying. The opposite is a "shift" response," which is a statement that shifts the conversation back to you.

If your friend complains about their annoying upstairs neighbor, you might say, "Yeah, you wouldn't believe what my neighbor's been putting me through. His party last night didn't break up until after 3 a.m." You've just shifted the conversation back to you and your concerns, rather than inviting your small talk partner to contribute even more.

A support response might be to empathize with your friend, or ask for more details about their neighbor's bad behavior and how they handled it.

In the right context, it is fine to use shift responses — other people want to learn about us, and we don't want to come across as withdrawn or secretive.

So many people make the mistake of treating other people's stories as openings for them to talk about themselves. But if you do that often, you miss an opportunity to learn more.

After a conversation partner contributes a thought or anecdote, we can say something like, "What excited you about that?" or "Wow, what happened next?" or "How did you feel when that happened?

Comments like these give your partner permission to expand on what they said or provide deeper insight.

The more you support what someone else is saying, rather than shifting the focus to your experience, the easier and more enjoyable small talk becomes.

Matt Abrahams is a lecturer at Stanford Graduate School of Business, the author of "Think Faster, Talk Smarter: How to Speak Successfully When You're Put on the Spot" and "Speaking Up Without Freaking Out," and the host of Think Fast, Talk Smart The Podcast. Matt received his undergraduate degree in psychology from Stanford University. Follow him on LinkedIn.

Don't miss:

Want to earn more and land your dream job? Join the free CNBC Make It: Your Money virtual event on Oct. 17 at 1 p.m. ET to learn how to level up your interview and negotiating skills, build your ideal career, boost your income and grow your wealth. Register for free today.