Wikipedia says Isaac Asimov wrote 506 published books. Where did he get his ideas? Charles Chu says Asimov used a number of tactics:
1. Never Stop Learning
"All this incredibly miscellaneous reading, the result of lack of guidance, left its indelible mark. My interest was aroused in twenty different directions and all those interests remained. I have written books on mythology, on the Bible, on Shakespeare, on history, on science, and so on."
2. Don't Fight the Stuck
"I don't stare at blank sheets of paper. I don't spend days and nights cudgeling a head that is empty of ideas. Instead, I simply leave the novel and go on to any of the dozen other projects that are on tap. I write an editorial, or an essay, or a short story, or work on one of my nonfiction books. By the time I've grown tired of these things, my mind has been able to do its proper work and fill up again. I return to my novel and find myself able to write easily once more."
3. Beware the Resistance
4. Lower Your Standards
5. Make MORE Stuff
6. "By thinking and thinking and thinking till I'm ready to kill myself."