First off, a quick reminder: the only eternal storytelling hard-and-fast truth is that there are three questions every story must answer.
1.) Who wants what?
2.) Why can't they have it?
3.) Why do I give a shit?
All other bits of writing technique are nothing more than hard-won advice, and YMMV.
I have to admit, John Truby's The Anatomy of Story utterly defeated me. I found a lot of useful tools in there, but at the same time nothing I didn't find in Elizabeth George's excellent book on general writing, Write Away. To boot, George has a nimble, engaging authorial voice while reading Anatomy is like having someone bang your temple with a ballpeen hammer all the while humming the opening four bars -- and just the opening four bars -- of "Holly Jolly Christmas" over and over again. Forever. I understand Truby's a hell of a lecturer, but damn this thing's a hard slog.
Truby rejects the current ubiquitous sequence approach to screenwriting. I think there's an excellent argument to be made on over-reliance on these structures; each screenplay is like a snowflake: unique and ultimately destined for a slush pile. However, being able to see the broad moves within your work, using these structures as a handle on the sheer bear of bringing a film over the finish line ... not a bad thing. At the very least they allow you to localize discussion when wrangling notes with executives. The fact that I began what passes for my writing career in television probably colors my opinions on the matter. I like a good act break, a little shove into the next section of the story.
Recently, I banged out a second draft beat sheet for a movie I'm working on, trying to isolate what worked in the puke draft and what might shift if I made some changes. I printed each sequence of roughly 4 or 5 story beats on a separate page, and laid them out on the table. My movies tend to then roughly lay out to 8 or so sequences, each with their own sub-goals and tones.
I realized, as I looked the pages over, that I'd reversed the third and fourth sequences (or the first two quarters of the Second Act). Then I stared at it for a moment. This was right.
I originally had the characters making a logical decision based on what was happening, make a run for some resources, and then head on off to the larger goal, enjoying misadventures along the way before being grievously interrupted at the midpoint.
What the accidentally shuffled, isolated sequences showed me was that if I allowed the larger goal to drive them, and then had them discover they needed the mini-goal along the way, this gave us a twist and a new bit of suspense. The larger goal created context rather than just being an endpoint. I could also see that if such a shuffle could occur without grievously changing my villain's plans, then my villain's plans were too vague.
Also exposed: the entire conflict of one sequence relied on it occuring after the other. I was, in fact, cruising on momentum there. (hey, I said it was the puke draft) Its internal structure was ill-defined. We've discussed books treating screenlays as essentially fractal before, and this shuffle reminded me of that idea and prompted me to break out some different tools.
All this to say -- try it. Grab your sequences or acts. Bang them out on separate pieces of paper. Line them up, face down. Shuffle them. Then flip them, and ask yourself: is this mini-story something worth watching on its own? Are its conflicts clear, its visuals unique? Who wants what, why can't they have it, and would I in theory give a shit for the next 12-15 minutes?
It's a nice way to get some altitude on the script, particularly when you've been knee-deep in the trenches for a few weeks.
(I also like to pick a representative color for each sequence, but that's my artsy bullshit kicking in)