View Website Using HOSTS file?

Hey. Got a new server, and need to test it b4 moving the existing sites. Disabled mod_user/whatever and now .php pages do not load. Get the 'Not supported' error. Supposedly there is another way to do this using the etc/hosts file........and/or the personal hosts file on the computer you're trying to test the site with. But instructions are vague and unclear...... Anybody got examples/clear instructions for doing this? z