Debugging hooks that fired?
Unless you get a fatal error (or blank screen) it's pretty easy to get a list of modules that will invoked when a special hook is called:

$modules = module_implements($hook);
foreach ($modules as $key =&gt;  $module) {
  $function = $module . '_' . $hook;
  if (!function_exists($function)) {
    unset($modules[$key]);
  }
}
// $modules is now an array containing all the modules that will be invoked by $hook.


You could use stuff like xDebug to track the flow of the Drupal, but this can be overwhelming, especially if you are new to Drupal.