There are lots of filmmaking tips and lectures out there, but typically they are for narrative or fiction films, which can be difficult to apply with documentary filmmaking. But here’s a good lecture about editing, that I think has good lessons for documentary editing.
The main principle is that each scene needs to have someone or something change, and that change is what makes viewers “lean in” and pay more attention. In documentary, after you’ve already collected all your footage and you are building a story around that, one way to create change is to edit from wide shot to close ups, from b-roll movement to still reflection.
During editing, whenever I’ve run into an important moment in an interview, I like to visually emphasize that important moment by avoiding distracting b-roll that visually says something else. So, apart from showing just the interview, I go to a close up of the subject in a b-roll shot (of them ‘reflecting’ and not talking), or a close-up of an object or hands, or a steady shot of a scene that emphasizes the reflection or thought. This is why you shoot rack focus close-ups of leaves, trees, buildings, out-of-focus subject walking away – for these moments.
Music is important too, obviously. But when you’re collecting b-roll, the important thing is to shoot as wide variety of focal lengths and shots as possible, so you can cleverly illustrate the change that comes through in the interview.