I'm looking for words or short phrases that show I'm paying attention to what the other person is saying in casual conversations, or words or short phrases to say during pauses in between exchanges that show I'm listening to have a smooth flow of discussion. I came up with the following:

Is it? Do you? Are you? and the like

Are the following also OK? I'm not sure, though.

I agree.
I understand.
That's true. That's correct. That's right.

OK or right or alright (instead of 'yeah')

Could you please give example should you have more?
By the way, what are these commonly called in English? Filler words/phrases?
I'm following. I'm with you.

I would prefer to be quiet and let the other person talk. A nod of the head would work as well.
Thank you. That was really helpful.

I'm sometimes worried about just being quiet, nodding my head, and saying nothing at all for a long while in such a conversation because the other person might think I'm not interested. I was thinking it would be better to utter short phrases, at least, from time to time.

I asked because it's difficult for non-native speakers like me to keep a conversation flowing smoothly.

I would really appreciate your ideas or suggestions should you have more.

Other opinions as well are very much welcome. Emotion: smile
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It might be a good plan to formulate a short simple question about the topic being discussed. Have it ready in case a pause occurs. That way the speaker will truly know you're paying attention.
The short quips will usually be spotted as artificial - unless the guy is so self-absorbed he's not listening to you. In that case, it doesn't much matter what you say.
It would be wiser to practice with a friend than with a stranger.
Thanks, Avangi, for your suggestions. I'll take note of them.
AvangiIt might be a good plan to formulate a short simple question about the topic being discussed.
I believe this is great for formal situations like interviews, meetings, etc. However, if it's just those casual conversations, it's hard to prepare questions beforehand.
AvangiIt would be wiser to practice with a friend than with a stranger.
I often practice with a friend, but sometimes I run out of words to say and saying the same filler words or phrases makes me sound boring. Emotion: sad
Anonymousgive examples
The most common one is "uh-huh", said with the mouth open or closed. In the latter case, it's more like "mm-hmm" Even just "mmm" is enough. Over and over and over; every time the other person pauses. No one will think you're being repetitious or boring. They'll barely notice, but they'll feel you're paying attention.

If what they say seems to ask for sympathy or agreement, keep saying "I know".

Another thing you can do, just to keep the conversation going, is to repeat, with a questioning tone, the last word or phrase the other person has just said. You can keep them talking for hours that way!

"Them": blah, blah, blah, blah, blah, because she was tired.
You: Tired?
"Them": Yes, she ..., blah, blah, blah, blah, and maybe end up in the hospital.
You: Hospital?
"Them": Of course, because ..., blah, blah, blah, ... except for my sister.
You: Your sister?
"Them": Yeah, she's ..., blah, blah, blah, ... until tomorrow night.
You: Tomorrow night?
"Them": ... blah, blah, blah ...

Well, you get the idea. Emotion: smile

Students: We have free audio pronunciation exercises.
Aha, I got it. That was really a great idea! Emotion: smile

While reading your post, I imagined myself doing or saying those you suggested. Great help. Thanks, CJ.