When I don’t want to listen to something which someone wants to talk about depends on the person:
1. Someone I know: Then most likely I will actively listen, because I understand it is investment in them, it helps them, and at a subconscious level they appreciate it.
2. Someone I don’t know: I tell them I have work to do, and I had better get back to it, or bring up whatever I have on my agenda to accomplish wherever I am.
How do I know when they aren’t listening, or aren’t interested? Body language, first and foremost, where are their eyes? You could throw in: “I brought an axe to kill you with” They will respond: “mmmmhm”.
I range this inconsiderate behavior on a scale: a slight foopah all the way to gross misconduct depending on how boring my topic is and how long I have been talking!
If you have been talking a while, then you might need to pause silently and allow them to naturally summarize…look the other party in the eye and wait…they will either catch up or confess they weren’t listening. Either way, you can continue, if you aren’t to offended.