Before going into that make sure you have the following items:
-A wireless router
-A notebook/laptop with wireless and LAN port
-A ethernet cross over cable
Once your VPN is set up and working on your Laptop you can proceed with the next steps.
Step 1: Plug your xbox 360 to your laptop using your cross over cable
Step 2: Make sure on your xbox 360 Dashboard your IP settings and DNS Settings are set to Automatic
Step 3: On your windows Laptop click on start and right click "Network" and select Properties, this will get you to your network and sharing center
Step 4: Click on "Manage network connections (on the left side of the window)
Step 5: Right click on Local Area Connection and select Properties
Step 6: Select "Internet Protocol Version 4 (TCP/IPv4)
Step 7: Make sure you click "Use the following IP address"
Step8: Give it the following IP address 192.168.0.1
Step 9: Subnet mask 255.255.255.0
Note: Default gateway: make sure its blank
Note: Preferred DNS Server make sure its blank
Note: Alternate DNS Server make sure its blank
Step 10: Right click on Your VPN (Virtual Privet Network) and go to its properties
Step 11: Click on the sharing tab and select "Allow other network users to connect through this computers internet connection"
Step 12: Right under allow other network users should be Home network connection a drop down menu select Local Area Connection and NOT YOUR WIRELESS CONNECTION
Note: Make sure "establish a dial up connection" is not marked and "allow other network users to control" is unmarked
Step 13: Make sure your laptop is connected to the internet via wireless internet connection and then connect your VPN
Step 14: Once that is done do a network test on your xbox live (Test Xbox Live connection) it should go all the way through