This is my note on useful commands/keybindings to memorize three years ago.

Most are obsolete because I'm more skillful now.

Basically I use fewer but more powerful plugins. I write Emacs lisp if there is no suitable plugin.

Three years ago, column edit,

C-x r t yourstring RET (See "How to do select column then do editing in GNU Emacs ?"")

Now I use Evil

Three years ago, save current position to register and jump to the position,

C-r SPC to save, C-j to jump (better-registers.el required)

Now Evil.

Three years ago, save frame configuration to register,

C-r f (better-registers.el required)

Now workgroups2.

Three year ago, (un)comment line,

M-; (qiang-comment-dwim-line required)

Now evil-nerd-commenter.

Three years ago for visiting the next/previous error message after compiling,

"M-g M-n" or "M-g M-p"

I'm still using it.

Three years ago, find-tag/pop-tag-mark

"M-." and "M-*"

Now Evil

Three years ago, grep current work directory only or all sub-directories

M-x lgrep/rgrep

Now grep in shell plus percol

Three years ago, visit multiple tags table

M-x visit-tags-table

hack tags-table-list directly might be simpler.

Three years ago, set countdown timer

M-x org-timer-set-timer, C-c C-x ;

Now I don't push myself with the timer thing.

Three years ago, mark subtree in org-mode

M-x org-mark-subtree

It was used to select the text to post to my blog.

Now I use org2nikola. The org-mark-subtree is hardcoded into org2nikola.