
This tutorial explains how to easily create the skeleton for a plugin. The tutorial assumes you are working within the elgg directory structure on your local machine and that you will ftp the code to your remote server later on. You could create the plugin anywhere you want as long as you ftp it to the correct location on your server.
Plugins are always placed in the /mod directory. Create a subdirectory there and give it the name of your plugin. This is what will show up in the Tools Administration section of Elgg.
In /mod/<your plugin name>, create an empty file called start.php. If this file exists, Elgg will load your plugin. Otherwise, you will see a misconfigured plugin error when you enable it.
See Manifests. The manifest file describes who wrote the plugin, what it does, what version it is, and under what license it was released.
That's it!