Here is one place you can start if you are looking for basic info on creating a plugin:
Create a file in the plugins folder. Call it whatever you’d like.
Place a comment block at the top like this, filling in the info specific to your plugin:
<?php /* Plugin Name: My Plugin Plugin URI: http://blog.kennyray.com Description: This is a plugin Version: 1.0 Author: Kenny Ray Author URI: http://blog.kennyray.com License: GPL2 */ ?>
At this point, you will see your Plugin in the plugins section of the site admin.