command line - How can i automatically execute a script after automatic boot?

I've recently opened a VPS running Ubuntu server 13.10 x86 (with no graphical desktop) in order to run a game server. Since it's a VPS there's a risk that the node may crash when I'm not watching. This means I may want to have the server execute this script automatically when the server boots. How can I do that? Another problem is that it seems to require a username and password after boot.