Record and play macro

Macros automate repetitive edits in vim

qa  (record into a)
q   (stop)
@a  (play)
10@a (play 10 times)

More vim commands

Show line numbers

:set number

Toggle line numbers on (use :set nonumber to hide)
Split window and open file

:vsplit other.txt

Vertical split; use Ctrl-w + arrow to navigate panes
Save and quit

:wq

Write file and quit vim
Quit without saving

:q!

Force quit discarding all changes
Global search and replace

:%s/old/new/gc

Replace all occurrences interactively (c = confirm)