In what way should one respond?

Imagine a day-to-day converation, in which someone is telling you something or just simply talking. At some point, what would you say to show you're interested, for the sake of being polite, even if you're really not?

For example, a girl was talking about her class activity this afternoon. She said, "We are planning to make a magazine... this way, it's gonna turn out perfect." During the time I was listening, I would say 'ok' a few times, my usual way of saying 'that's interesting, keep going'.

Is there anything else I can say instead of that? Thank you.

Just add a few "umhmh" (like a mouth-closed uhhuh), and "uhhuh" sounds from time to time, too. Depending on what's being said, perhaps a few "goodness gracious", "good golly", or "holy cow"s could also be added from time to time.

"perhaps a few "goodness gracious", "good golly""

rofl you do NOT want to say anything of the sort. a few "wow", "really!" "cool" "mmhmm" "no way!" and remember to laugh whenever the other person laughs. Or you can tell them that they're boring you out of your mind.

If you're not interested, why not latch onto something that she says, and say "that reminds me of the time when..." and then give a long, rambling story that transitions into a new topic to change the subject. Then you can talk about something more interesting. I've rarely seen someone who could convincingly feign interest in something that bored them to tears.

Or why not just ask them if they want to see the latest additions to your bottle top collection, along with a detailed explantion of where they came from and the precise chemical components. They will probably excuse themselves in a hurry. In my experience, boring people tend to be afraid of being bored themselves.