Here are three Emacs tips that I seem to have a hard time remembering. I’m posting them here to help them stick to my brain.
Align
Emacs has a number of powerful align commands, but most times the following incantation will suffice to magically align text into neat columns:
C-u M-x align
Repeat
I don’t know how I manage to forget this handy helper, but I do. The following will repeat the most-recently executed command:
C-x z
Continue hitting “z” to continue repeating.
Recursive edit
While you are in the middle of doing something in Emacs, such as a query-replace-regexp, you can put that something on hold, do some editing, and then return to what you were doing. This maneuver is accomplished with Recursive Editing. In short:
C-r
(enter recursive edit)C-M-c
(exit recursive edit)C-]
(abort: exit all nested recursive-edit sessions)