The following list of example rules can be setup via WHM -> cPanel Varnish -> Advanced Configuration -> URL opt-out
1) ^/wp-admin
The carret means match a URL starting with /wp-admin
Example: matches http://blog.unixy.net/wp-admin and http://blog.unixy.net/wp-admin/index.php but does NOT match http://unixy.net/blog/wp-admin
2) /wp-admin (without the carret)
Matches any URL that has the string "/wp-admin" like http://unixy.net/blog/wp-admin or http://unixy.net/anotherblog/wp-admin/login.php
3) ^/index\.php?action=googlemap$
The above rule matches exactly any URL: http://blog.unixy.net/index.php?action=googlemap
If the above URL were to be "http://blog.unixy.net/index.php?action=googlemap2", the URL would not match.
Note: dots (.) must be escaped! Example "update\.php"