How to do I do X in emacs

People use emacs for a range of activities. So whatever you want to do, there's a chance that someone has already done it. Your first point of call for extending emacs should probably be `emacswiki`, which lists emacs extensiosn that you can use for different activities.

It may also be worth checking MELPA and ELPA, the emacs package archives directly, since useful packages can go undocumented on emacswiki. If you find nothing there you might like to search github directly.

Reading existing libraries

• Check load-path variable to find where files included from.

Writing functions that can be executed from Emacs

• Use of (interactive) to make the function callable