Theory and complicated stuff on why and what NS records are.

http://www.zytrax.com/books/dns/ch8/ns.html

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Requirements:
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Owning a domainname and signing up for a service like zoneedit.com for example.

Having the domainname using the nameservers that zoneedit.com gives you.

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Create NS records:
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On zoneedit.com add a zone: aka your domain name.

Don't use webforwards to get a browser to a location, use actual IPs. The reason for that is so that you can't get adds somehow hijacking your webspace.

You can have as many subdomains as you want.
The awesome part about this is that even though a website you can't access outside of your network is running on the internal, you can use the full qualified name on a smaller, limited scale.