While it isn't a video, RNT has a 3 CD collection about duck calling. The 3rd CD in the set, I think the name is Advanced Techniques, talks about what to do and when to do it. You'll hear them say, and it is probably true, that this can only come from time spent in the field. Trial and error.
"I'll start spending less time with my dog and more with my wife when she starts fetching ducks for me"