While looking how to to customize the cart view in
Virtuemart 2.0, I've come across with this simple step-by-step explanation:
What's new in VM2.0? Templates!
Fantastically easy! Just copy the component views files into your
./debugtemplate/html/com_virtuemart/<component> directory and code away.
For instance, to give your checkout page a different look, just copy components\com_virtuemart\views\cart\tmpl\default.php into ./debug<your template>/html/com_virtuemart/cart/default.php and hack it.
Actually this follows the MVC Joomla! extensions pattern, so one can apply this customization technique to any component.
./M6