PAM configuration for password-less login

I just started adventure with PAM. I was thinking about configuring system in way people use Windows. No one from person I know is using password on Windows. I also imagine to install Slackware for person who knows only Windows - no passwords would e nice.

The conditions are very basic. Members of users groups are allowed for password-less login if they have home directory and set shell.

For root password is required.

I am not asking for perfect solution just something which works.