How to switch from wp-cron to server cron?

Apparently there is a huge problem with wp-cron being spawned multiple times which will overload your server. Everywhere on the web is saying switch to the server cron instead. So I added define('DISABLE_WP_CRON', true) to the wp-config. My issue is how do I add the cron server? I tried add this /usr/bin/php /home/username/public_html/wp-cron.php, but I get an error saying:

Status: 302 Moved Temporarily
X-Powered-By: PHP/5.3.6
Location: http://mydomain.com/wp-signup.php?new=
Content-type: text/html

What is the correct way to do this for a multisite setup?