Using Drupal Commerce, how do you render the "add to cart" button? I have created a custom node.tpl.php file for the product_display content type. I have everything worked out except I have no ideal how to isolate the "add to cart" button, actually the "add to cart" form, and render it within the template wherever I need it.
The product reference itself renders as the button. In your product display content type, make sure the product reference has the "Add to Cart form" format, then render it thus:

&lt;?php print render($content['field_product']); ?&gt;