that's pretty much it. It's usually better to use absolute paths ie., /srv/www/public_html/includes/fetch.php but on shared hosting that might not be an option so ../file.php works just as well.
I have to agree. However, if for some reason the site has to be moved, the use of $_SERVER['DOCUMENT_ROOT'] instead of the /srv/www/public_html may be better. I usually put this into a constant called ROOT: include_once(ROOT . '/includes/fetch.php'); .
Mind you, placing a variable into a constant may be a bit suspect.