Another nifty tool is vi editing mode. You run "set -o vi", and now your shell takes vi modal editing commands. That along with Ctrl-r for reverse history search has made life in the shell so much easier. Bash has a ton of little stuff like that built in. Zsh has a few more.
:w !sudo tee %
" Let :w!! gain sudo privileges without closing and reopening vim
cmap w!! w !sudo tee % >/dev/nullhttp://stackoverflow.com/questions/2600783/how-does-the-vim-...
Also, after you have entered a previous command, to edit it, or any previous command in the history, the first thing you have to do is press ESC (to go to command mode) and then k, thereby bring the last entered command into view for editing.
When editing a command, but in command mode (not insert/append mode), you can also press v to open the command in vi(m) in a temporary file, then have the full screen editor at your disposal to edit the command (useful for long scripts including for/while loops or long pipelines), and then when you save and exit (:wq or :x followed by Enter), the newly edited command gets executed by bash.
Also, this editing technique is useful not only for correcting typos in commands, but for modifying a previous correct command, to change some words in it and then re-issue it.