initializing a blank DVD+R disk?

[Stuart McGraw]

I am trying to setup backup software (Bacula) on my home
network and ran into a real dumb newbie DVD question I haven't
been able to google an answer to (at least an answer I could 
understand) since I have never used writable DVDs before.

How does one write a iso filesystem onto a blank DVD+R disk 
without writing any files, and leaving the DVD writable (i.e,
not finalized if that this the right term)?  The growisofs 
and mkisofs man pages are mostly greek to me.  Is there a 
magic cookbook incantation I can use until I can figure 
out all the techy details?