Posted 2007-05-22, updated 2021-07-01.
These are some emacs keybindings (and other functions) that I once found useful. I’ve mostly used Sublime Text for the last few years, however.
C-[SPC]: set mark
C-x C-x: exchange point and mark
C-w: kill (AKA “cut”)
M-w: kill-ring-save (AKA “copy”)
C-y: yank (AKA “paste”)
M-h: Put region around current paragraph (mark-paragraph).
C-x h: Put region around the entire buffer (mark-whole-buffer).
C-u C-[SPC]: Move in mark ring
M-d: Kill word
M-[DEL]: Kill word backwards
C-M-k: Kill the following balanced expression (kill-sexp)
C-x r r: Save position of point in register r (point-to-register).
C-x r j r: Jump to the position saved in register r (jump-to-register).
C-x r s r: Copy region into register r (copy-to-register).
C-x r i r: Insert text from register r (insert-register).
C-x r m [RET]: Set the bookmark for the visited file, at point.
C-x r m bookmark [RET]: Set the bookmark named bookmark at point (bookmark-set).
C-x r b bookmark [RET]: Jump to the bookmark named bookmark (bookmark-jump).
C-x r l: List all bookmarks (list-bookmarks).
M-x bookmark-save: Save all the current bookmark values in the default bookmark file.
M-` shows the menu.
M-x highlight-changes-mode toggles showing the changes you’ve made to the file since the last save.