[How Delivery.log Works?]

You can enable the delivery log in the site configuration file, for example:

[deliveryLog]
enabled=1
name="log/delivery.log"
fileMode=0644
priority=6

The "name" path is relative to your Revive install "var" folder. So the log will go to, for example if Revive is at /var/www/revive_adserver to

/var/www/revive_adserver/var/log/delivery.log

You'll also need to make sure the folder exists and is writable by your webserver user, for example if the webserver user is www-data

mkdir /var/www/revive_adserver/var/log

chown www-data:  /var/www/revive_adserver/var/log

After that the logs with the appropriate log level can be seen in delivery.log there.

[How to block / not count HTTP HEAD requests?]

I prevented HEAD requests getting to Revive by adding a rule in Nginx:

    # Avoid HEAD requests triggering click hits
    if ($request_method = HEAD) {
        return 405;
    }