What I really want to do is to be able to do whatever I want. Haha. Seriously, I want to be able to customize Drupal so that it doesn’t look like Drupal. So I am now working on theming functions. And to find out how a particular part of my site is generated, I am using the Devel module along with Devel Themer. These used to be packaged together but now they are separate contrib modules.
I had a sort of hard time getting Devel_themer to work properly. It was on the harder side of medium as far as modules go. But, I paid close attention to the issue queue at Drupal.org for the Devel_themer module and I was able to get it all figured out eventually. If you are getting 404 AJAZ errors, look at the queue and you will find answers there.
Lullabot has some good videos on how to use Devel_Themer. Check them out here.