Setting up a home web server is simple. If you do it though, check and make sure that your ISP allows you to do so. Here is my recommendation to begin:
1. Register your domain name with godaddy.com, register.com or whomever you choose (ie.www.xyz.com)
2. Determine whether you will have a public dynamic IP address (will change constantly) or a static ip address (usually have to pay for this from your ISP)
3. DNS Setup
a. If you are using a public dynamic IP address (which I am sure you are in this case), then set up a dynamic dns free account (go here - http://www.dyndns.com/services/dns/dyndns/). You will need to set up a username and password, which you will later use on the DynDNS Updater you will need to install on your Windows web server. Create the zone for your domain (ie. xyz.com is a zone you create).
b. If you are using a static IP address, then make sure the name servers are 'Parked' with your domain provider, then set up a forward to the public static IP address of your home network (from here, you just set up port forwarding in your router/gateway to your web server and you should be done)
4. Web Server Configuration
I. set up a 'static' ip address on your network card which will manage the incoming connections. Make sure that IIS is listening for requests through this IP address via IIS Manager.
II. If you are going to use the dynamic dns configuration for DNS, then download the DynDNS Updater app to your windows server and it will manage the connection between your web server dns and dynamic dns servers (this is cool and easy)
III. Set up a test index.html in IIS Manager for your 'Default Site'. Open a web browser and open 'http://localhost' to make sure you can access the site.
IV. Make sure your Windows firewall allows traffic through port 80.
5. Router / Gateway Configuration - go to 'Port Forwarding', and forward all requests via port '80' to the static IP address of your webserver (ie. Allow Incoming Port '80' to 192.168.x.x')
6. From your web server, Go to 'http://www.whatismyip.com and see what your public ip address is.
7. Once your IIS is set up, your port forwarding has been configured, and dynamic dns is updated, ping the domain you registered 'ie. www.xyz.com' and see if it matches the IP address of your web server public ip.
8. From outside your local area network, try to access your domain 'http://www.xyz.com'. If success, then you are good to go. If no success, review all these steps again.