>I want to make "daily digest" the default for my list.  How do
>I go about this?  I think I need to edit the header, but how?
 
In your list header, enter or add DIGEST to the Default-Options keyword.  If
this is your only default, it would look like
 
DEFAULT-OPTIONS= DIGEST
 
Users that didn't like this option would send the command SET listname MAIL
or SET listname INDEX.