If you write fiction long enough, interviewers will start to ask you “Where do you get your ideas?”
Readers love this question (it’s also a dreaded chestnut of con Q&A panels). Writers hate it. It’s like asking “Where do you get the time to write?” Every one of us gets the same 24 hours each day; doctors spend some of those doctoring; drug addicts spend some of that getting high; writers spend part of one of those hours writing stories. One person can be any or all of those, and more.
Likewise, we all see/hear/mis-hear/read/misread/imagine all sorts of crazy crap every day. Those are ideas. That’s where ideas come from.
But that’s maybe a cheap answer, because it takes the question too literally. I think maybe what folks are asking when they ask “Where do you get your ideas?” is “How do you store/catalogue all the weird shit you see every day so that it’s useful to you later?”
And to that, my answer is this:
My brain locks on to odd shiny things and hordes them.
Most of the fiction I write comes out of a collision: I’ll stumble across some interesting fact or idea or snatch of plot or dialogue, but won’t really have any use for it, and so it just sorta bobs around in my head. Sooner or later, as other shiny ideas catch my notice and get tossed into that cranial junk drawer, several will bang together and stick in some interesting way. When ideas stick together they make a distinctive POP!ing sound. I listen for the pop, then start writing.
This is the essence of the “magpie and junk drawer” approach to research and writing. I stumbled into it as a kid having to do research papers, and it’s served me well ever since. Go forth, apply this in your life, and sin no more.