How to disable USB automounts

[Itay <debian@itayf.fastmail.fm>]

When I stick a USB device into the socket it is automounted; KDE pops 
up device notification widget, file manager window, etc.

I tried to disable it:
KDE -> System Settings -> Removable Devices, and unchecked
"Enable automatic mounting of removable devices".
This didn't have any effect.

In fact, I would like to disable automounts for all users.

I found in this thread two (contradicting? redundant?) advices.
http://www.linuxquestions.org/questions/linux-newbie-8/disabling-usb-automount-kde-891757/

1) To remove the user from plugdev group.
   (But how to avoid future new users from being added to that group?)

2) To disable automount in udev rules.
   I don't understand udev at all, and couldn't locate the actual
   lines that I should comment out.

What would you recommend me to do?
I would appreciate if some details will be provided (which lines to 
comment out, which files, etc.)

Thanks in advance,
itay