Correct Way To Disable Loading A Module?

[bill g]

Not being well-versed in Debian, I need to ask how to stop loading a
kernel module I don't want to load.

Specifically, I use an Nvidia card and the Nvidia driver.  I want to
enable  Nvidia's agpgart via an optional xf86config, but don't know
how to avoid loading the other module.  It isn't listed in
/etc/modules.  It is listed in modules.conf, which warns to avoid
editing the file and to use update-modules instead.  However, "apropos
modules" shows update-modules is outdated.

What's the correct way to do this?

billg