Theme Custom Pages

You can use wordpress templates to load for a particular page.
just create a template file with any name ( place template definition in file i.e commented code to declare a template) and select it as a template while adding a page.
in this way file will be loaded automatically for page and you can use that template for other pages also.
add following code at top of you file

<?php
/**
 * Template Name: My custom template
 *
?>