If you're considering adding NAC to your network, you're most likely interested in some form of endpoint compliance. If you want to include endpoint compliance as a requirement for getting access to the network, you need to first decide what makes a device compliant.
Consider looking for antivirus software, anti-spyware software, firewall software, and operating system patches.
When you create this list of compliance requirements, make sure you consider the following devices:
Guest machines
Corporate machines
Contractors' machines