How to prevent loading some LaunchDaemons?
On boot all plist files in /Library/LaunchDaemons are scanned. The plist files which contain 

    &lt;key&gt;Disabled&lt;/key&gt;
&lt;false/&gt;


are loaded.

When you want them to not be loaded during next boot, change &lt;false/&gt; into &lt;true/&gt;.

For exemple with terminal command $ sudo nano /Library/LaunchDaemons/com.google.keystone.daemon.plist

The built in command which prevents loading a daemon on next boot and immediately unloads (stops) the requested daemon is called like this:

$ sudo launchtl unload -w /Library/LaunchDaemons/com.google.keystone.daemon.plist


The -w switch makes that  is being written into the plist.
The -w switch makes that the daemon is not loaded on next boot.

To verify that the daemon is unoaded with succes, issue:

$ launchtl list | grep com.google.keystone


Should return something like:

-   0   com.google.keystone.user.agent


When the output line starts with a "-" (minus sign) then the unload succeeded. 

12132   0    com.google.keystone.user.agent


In case there is a number (the PID) at the first position than the unload failed.