To start with, you should know that I'm currently working with the default Amazon AMI install, which is pretty much a basic CentOS install as far as I can tell. Things shouldn't be much different for other version of Linux, such as Ubuntu or FreeBSD. I should also note that Varnish is currently not compatible with Windows platforms, which is annoying for me as I use a Windows test server at home, and at work.
Let's get started. First of all you're going to have to configure your Apache server to run from a different port. The examples below show port 8080, but you can choose any port you like.Listen 8080