Tony Ballantyne is an Emacs-using Science Fiction writer whom I’ve written about before. Ballantyne has an interesting device to help him remember Emacs commands: the Emacs workout. The idea is to write short summaries of Emacs features that you find useful but don’t invoke every day. That way, you can periodically go through the list to build up your Emacs muscles. Used correctly, the technique is an example of spaced repetition, which many claim to be the most efficient way of learning something. See this excellent video by Ali Abdaal for more on the idea.
You can find Ballantyne’s list at the link. It’s worth reading to pick up some new ideas as well as remind you of old ones. For instance, I didn’t know about map-query-replace-regexp. I don’t have a need for it in my workflow right now but it’s nice to know about it for the day that one pops up.
Ballantyne’s list is a useful place to start but to really take advantage of the idea, you should make your own covering the seldom needed but useful Emacs techniques that you can never remember. That way you can review them periodically and keep them fresh in your mind and muscle memory. There are all kinds of useful shortcuts that I learn but forget because I don’t need them often. I even have functions that I’ve written in my init.el that I’ve either forgotten or only vaguely remember. You can, of course, look these things up once you know they exist but that’s a serious context switch. I’m going to try Ballantyne’s method to see if I can better keep them in mind.