Server 2003 Shares

I recently was put in charge of win2003 server. The network user share
for this 40 seat environment was implemented with virtually no security.
In other words, all users have access to all other network users home
folder. How should I approach locking this down? Do I need to change
the permissions on each share to allow access for the owner of the
chance, or can I do this through some sort of blanket permissions?

THanks!