Configuring vhosts
 

So I am new to vhost, the Apache documentation makes it look oh so easy. So I decided to give it a try. I put some domains and run with it but I got a DNS error.

Should I need to previously enter this domains on my /etc/hosts and if so, should I disable squid too?

DNS has nothing to do with virtual hosts. if you're having DNS issues, then it's your responsibility to fix that, as without that working apache is not going to be contacted at all. as you've guessed for a quick local hack, just add it to the hosts file. squid should have nothing to do with this either, as long as you don't use a proxy whilst testing. i'd suggest using the curl command line tool to check lower level web things out.