Believe it or not, putting down books, stepping away from screens, and just getting the blood flowing through exercise is a great way to clear the mind and just

Believe it or not, putting down books, stepping away from screens, and just getting the blood flowing through exercise is a great way to clear the mind and just let it wander. I'm also reminded of walking meditation. Used to work with a math PhD who would take breaks to walk around the parking lot smoking his pipe. Other than that, I hang out in forums like HN and certain subreddits that seem to spark ideas in me. Some of them are hobby specific (I've got at least a dozen ideas for apps for search and rescue), but some just come out of left field or I look for a problem I have and want to solve. I will also add that I use org-mode and live in emacs, so taking a note is just a couple of keystrokes away, and disk storage is cheap. I can always just archive it later, so I've never liked the idea of throwing out so-called useless ideas (was from some time/task management system, can't remember which), as I can always set the state to CANCELLED.