First, I read widely, and I ponder what I've read. That keeps ideas flowing. By widely I mean outside my normal areas of publishing. Other books open up for me a world full of fascinating people and ideas.
When I was in graduate school I promised myself that I would read at least one book a week. I've held to that. When I read, I ask questions, which the author doesn't always answer. I might read a chapter and think I have a better idea or could state the same truths more clearly. (If we're going to write, we have to have a certain amount of ego involved.)
Second, I'm attracted to people who are as bright, or brighter, than I am. When they tell about books they like, I'll look into them. Others' ideas stimulate me. My best friend, David, and I meet every week and open up to each other—and I can think of only one or two times when I haven't grasped a new concept or left with a different approach to an old idea.
Being in the presence of people who think deeply and who process information differently enriches my life and spawns new ideas.
Third, I'm open to new ways to see the world. Some authors say, "I'm curious," and I assume it means they're constantly asking questions and seeking to deepen their lives. That's a compact way to say it for me.
Ideas are out there waiting for me to find them.