Is it possible to stop sessions being saved?

[Chris Green]

I'm finding xfce's saving of my session a real pain, I want a *clean*
system when I restart, not on littered with junk from the previous
session.  Why else would I restart except to clean things up?

I have "Save Session for Future Logins" unchecked in the Logout screen
but it would seem that if I either shutdown or restart directly then my
sesison gets save.  

Is there any way to prevent this behaviour?  I really want the default
to be *not* to save any session information with the possibility that I
might occasionally want to save a session.

See also a separate message about terminal window placing.

-- 
Chris Green