It seems almost stupidly obvious, but I've never seen it phrased this way before.
Between scenes, insert the words, "And then..." if they fit, something is wrong with your scene.
They suggest that, "Therefore" should fit, giving a flow, or "But", when the next scene throws a wrench into the works.
This creates a much tighter flow between scenes, each of which builds on the last or throws a curveball, instead of one scene happening, and then something else happens, and then something else happens and so on.
For the full video (where they do a much better job of explaining it) see below. http://brassbolts.blogspot.com/2011/09/and-then-vs-but-and-therefor...