Get list of all the hooks your site currently uses

In includes/module.inc, find the module_implements() function (around line 715 in Drupal 7). At the top of the function, just add this below and you will get huge output of all the hooks that are called.

 

function module_implements($hook, $sort = FALSE, $reset = FALSE) {
  drupal_set_message("hook_$hook");
  ......