Let's say your component is called 'Awesome'
define('JPATH_ADMIN_AWESOME', JPATH_ADMINISTRATOR .DS. 'components' .DS. 'com_awesome');
@require_once(JPATH_ADMIN_AWESOME.DS.'helpers'.DS.'loader.php');
This is the minimalist code to include your component classes where you want.
Then the best is to check if the component exists, and do not execute anything if the component is missing.
Note : DS must be defined. You can use DIRECTORY_SEPARATOR instead.
Once your component loaded, DS will be defined.
Also : since and thanks to JLoader, when you include these lines, almost nothing is loaded in memory until you start to effectively instance your classes.
A jewel ...