It depends. If I'm writing a scene where the main characters do something that disturbs the peace, I look at things my friends and I did together, see what would work for the characters, and use that. Normally, my characters are rednecks, and my best friend is one, so we've done plenty of things to retell.
Other times, if I have a weird dream, or one that stands out, I turn it into a story. Once I used a dream because of how vivid it was, another . . . well, it was just plain freaky. When I was exchanging dreams with someone, it turned out recently we'd had nearly identical dreams. I've taken the things that were the same in both dreams and put them into stories before, but in long ones. Come to think of it, maybe I should do a short story version and post it here.
. . .
Uh oh.
My paranoia comes in handy, too. I've done plenty of stalker stories, so I just look at every day things and think of how they could be misused. Or, think of ways someone could attack me or kidnap me wherever I am. Keeps me on my toes and keeps my brain going. I go for lots of late night walks, and always hop into ditches to avoid being seen. I think about situations where you're being chased and need to do that, or if the traffic's heavy, I'll think of why that could be. Or, if the cars are speeding, I think of why they'd be doing that.
Then, the final weird one. I just get hit with ideas out of nowhere. It's usually not hard to tell when it happens, I'll just be doing something, and I get hit with an idea hard enough that my head jolts. It's usually when I've been trying to think of something to do with a story I'm working on, stop, then the solution arrives out of nowhere.
Pretty much anything does it for me, in other words.