Anatomy of a 
Committed 
Donor

This is not to suggest you can convert everybody. The majority of your donors are not committed to your organization, and while in theory many could be, in practice you have to make choices based on limited resources and the likely return. Therefore, pick a relatively small handful to target. There are "good" donors going off your file every single day. They, by definition, are either highly committed to your organization, uncommitted or somewhere in between. The good behavior/high commitment segment is an obvious place to start.