Add a section like this at the end of /etc/samba/smb.conf:
# A publicly accessible directory for all kinds of exports
[export]
comment = All kinds of exports
path = /export
read only = yes
guest ok = yes
guest only = yes
By default other Linux machines will be able to access this share,
but to make it accessible from Windows you must tweak the security option in smb.conf:
security = share
Make sure Samba service is running and listening on port 139.
netstat -ntl | grep 139/
Check on a Windows machine that the Samba share is visible
net view \\servername dir \\servername\export
To start Samba automatically at system boot (redhat):
chkconfig smb on