Image via WikipediaIf you have not read this lately, and I mean in the last year or so, the National Institute of Justice has done an outstanding job in the second edition of their guide for first responders.
You can download the guide in PDF format here:
Electronic Crime Scene Investigation: A Guide for First Responders, Second Edition
Whether you are in law enforcement or not, it is a valuable resource and contains some very useful information. The second edition is far better than the original.
They also publish some other very useful guides and publications.