Casting:
Snow casting
FBI resource
How to cast.
Another How to.
Evidence collection in general:
Evidence Collection
Digital evidence
BFRO tips
VGL site for collection
Collection kits
Various collection kits.
Witness interviews and written testimony:
Narrative indicators
Eyewitness Evidence (PDF file)
Interviewing Guide
Cognitive interview summary. (PDF file)
How to
Just some damn good ideas:
Can I get a witness
Posting your encounter.
Six things...