I have build script "Auto Installer Varnish Cache for Directadmin". Hope it can helpful for newbie want Varnish Cache running front Apache.
wget http://files.profvps.com/install-varnishcache.1.0.sh
chmod +x install-varnishcache.1.0.sh
sh install-varnishcache.1.0.sh
There is result when install completed and header response: 
If have any problem/issue when installing or running. please post here and i will support.
P/s: Sorry for poor english (come from Vietnam). There is first time i build script. Hope you like it.
Regards,