How can I make sure that newly created files in a shared directory are owned by a specific group?

In order to do this, you can set the shared directory's gid bit. The following commands should make any newly created files in the shared directory, /data/shared, owned by the group admins:

chgrp -R admins /data/shared
chmod 2775 /data/shared

Below is a sample session that illustrates the effect of setting the gid bit of a d...