I'm working on my course syllabi for next semester. I usually don't work on spring semester courses until late December, once the fall semester ends. But, being on sabbatical right now, I can prep ahead.
When it's time to refresh a course I've already taught, the first thing I do is review a hard copy of the syllabus from the last time I taught the course. I'm always happy to see how much I've marked up the syllabus. It's not rocket science, as they say. Simple notes like "this worked well," "this ended up taking two sessions," "change this up," "they liked this reading," etc. Sometimes I write "this could have gone better (see notes)" which directs me to my hard copy of the class notes with ideas of how the session can be improved. We know how badly it feels when a class session doesn't go the way we hoped. Sometimes we don't have to scrap the session. It can be a matter of minor adjustments. So I try to leave myself notes for ways to make a session better the next time. Same goes for paper assignments and other course requirements. Leave yourself notes after students submit papers and you've graded them. Were you happy with the paper length? Did you include a rubric (if so, was it effective)? Did you give students precise instructions? And so on.
The next thing I do is check a document in my electronic course folder. The document name is "New course ideas". I can work with these ideas to replace things that didn't work well in the previous semester.
Then, I check my email file for the course. That's the way I bookmark articles and videos. I have email files for all my courses. So when a friend or student sends something (or I send myself something) that I don't have time to read, watch, or process, I put it in the relevant course folder. That way I keep course materials fresh and interesting for myself and students.
Okay, time to get back to revising my syllabi.