Dian Schaffhauser in an article for Campus Technology did a good job in boiling down the emergency notification down to 7 key issues.

In a nut shell:

1) Know your resources (and alternatives)

2) Practice the Plan  (just like in elementary school)

3) Expect that decisions will need to be made based on incomplete information

4) Less people involved in decision-making is  better

5) Use multiple channels/modality for communicating

6) Define "emergency"

7) Layer your approaches to communications