In my theme's functions.php, I'm including a signup.php file which I want to use for all the signup setup and AJAX calls.
This file will be included at 'template_redirect'.
When I try to evoke an AJAX call, nothing happens. But instead, if I put the code directly into the functions.php file, everything works great.
So I'm assung that the action 'wp_ajax_...' is executed before 'template_redirect'. Is that right? This great article isn't too helpful for AJAX requests, as it's not clear which one was proceeded first.