If you are familiar to drupal zen theme then you will know how to create zen subtheme’s. But, what if you want to override the drupal’s default node.tpl.php?
First of all, you should install the theme developer module and then check what file you must replace. In this example we will override the /sites/all/themes/zen/modules/node.tpl.php with my custom code for theming a CCK node (content type=’product’). So, follow these steps (the subtheme name is called ‘mysubtheme’)
- Copy sites/all/themes/zen/modules/node.tpl.php to sites/all/themes/mysubtheme/modules/node.tpl.php
- Copy sites/all/themes/zen/modules/node.tpl.php to sites/all/themes/mysubtheme/modules/node-product.tpl.php
Please note that you have to also copy node.tpl.php to your mysubtheme subtheme modules folder. If the node.tpl.php file from zen is not copied into the sub-theme then the content type variants i.e. node-[content-type].tpl.php are not seen. Once the node.tpl.php is copied to the sub theme then all is good 
(took me a while to figure this out!)