Congressional Research Services (CRS) has put together a nice short (10 page) document, Congressional Primer on Major Disasters and Emergencies in which it explains the disaster declaration process, types of declarations and generally how the system works.
The target audience is Congress and the staff who work there, but the information is applicable across the board. It appropriately addresses the "fuzziness" of the declaration process and the latitude given to Governors and the President when it comes to declaring a disaster.
One bit of information I had not realized is that Individual Assistance (IA) grants are now capped at $30K. I remember when before Katrina they were $13K per household.
I also like the fact that the "Who is in charge?" question is answered with a short explanation of the principal of Federalism in emergency management. There is also a section on what a congressman or woman can do to help their constituents when disasters strike their districts.
I'd tuck this document away and dust it off when a disaster looms, or has impacted your region. It is an excellent primer for those elected and appointed officials who will be engaged in the disaster process.
Bill Cumming shared the link to the CRA document.