If you want to know how to hack, read the first few chapters of IIS Security by Marty Jost and Michael Cobb.
The book sellls for about 50.00 USD. It is one of my favorites. It discusses security and hacking methods,
One good method is to follow DaRK-RaiDeR-s' advice and use a firewall. Another is assuring that your system patches, service packs, are up to date. After you have done that you can disable all non-essential system services. You might want to put the root directory of your web sites content on a different disk or in a different directory from your web sites operating system to guard against a transversal attack. You remove unnecessary application mappings. You should probably modify your BIOS to prevent booting from removable media.

There are so very many things you can do. Get yourself a good book like the one I described.