[MacDV] Compression

[Timothy J. Luoma]

Excuse yet another clueless newbie question, but again I'm confused by  
what I read when I try to find answers for this in Google.  I'm not sure  
if I am asking the wrong way or if these are so basic that no one thinks  
about answering them.

Where can I learn more about how to compress video (i.e. get 2.5 hours on  
a 120 minute DVD) using either iDVD or Toast6 Titanium or whatever other  
program I should use?