A basic idea of how involved you are wanting to go would be the first thing to be determined. All out or hold on until the cavalry arrives.

Designated Incident Commander who would take charge.
The phone tree idea works, unless as with tonight's CS fire, cell tower down, causes service issues.
Logistics.
Who is handling communication with other EMS units, who directs traffic, trauma area, decon if necessary.
Food and liquids for consumption, separate area for restrooms, disposal of waste from area, trash containment, etc. Sanitary conditions for minor surgical procedures.
I have extensive hands on with decon's, DI water systems, sterilization techniques, cross contamination .

Tool accessibility
Chain saws, air compressors, generators, fire suppression and containment equipment, transportation, emergency lighting.

Security
Level headed folks to watch a secured area. Hand held radios so you know what the other hand is doing.
Clearly defined Identification, to determine who is who they say they are.