I was at the Wildscreen Festival conference in Bristol yesterday (a conference showcasing wildlife films and photography, equipment for said filming / photography, giving awards for said films/photographs, etc). It was interesting to hear Wendy Dark, previously head of the BBC Natural History Unit, outline key aspects of constructing wildlife documentaries. I can't remember all her points, but they included: show not tell; have a hook; and take the audience on an emotional journey. Sound familiar? The main way in which her advice differed from writing, IIRC, was in her recommendation to bring the audience out of whatever dark places you take them to -- don't leave them somewhere nasty. Maybe that's good advice for writing too, but I don't remember hearing that particular point expressed in a literary context.