Where does a writer get her ideas? Everywhere. A snatch of a conversation, an article in the newspaper (pinned to the board in the office is a whole wall of them!), a history book (oh my, history, yes!), or a memory. A hint of a song, a scent in the breeze, a new place. Travel awakens the creative juices like nothing except a quiet day at the beach, parked under an umbrella far from the cocoanut-scented crowds. Music can trigger a scene (Sting's Desert Rose), as can food. How often does a meal remind you of a gathering of fascinating friends, a romantic date, a miserable moment? Every moment of an everyday life adds to the creative well, into which you can dip whenever you want.
I knew a writer who said his ideas all came from the time before he hit 21. Since he was well beyond that age, I thought how sad it was that he felt his creativity ended so soon. Every day brings me something new, something I can mull and let steep in my head until I need it. Sometimes it's how an oak leaf clings to a branch day after day, or the way the moon shadows that same oak tree at midnight. I've been told I'm a visual writer, and I can see why. I "see" the scenes I write as they play out in my head like a slide show. Guess that comes from being an art history major in college - and memorizing millions of slides of works of art for identification purposes.
Writers pay attention, and that's the real secret behind where writers get their ideas.