I think for a novelist's purpose, one of the values in this podcast episode is learning about pacing. They discussed a two-hour film as a 120 page script. They break it down into three acts of 30 pages, 60 pages, and 30 pages. But percentagewise you can figure out the acts in your own novel page numbering.
One third into act one is your protagonist's fateful decision. That's when the character decides to take the quest or not.
So, I took a gander at C.S. Lewis's The Magician's Nephew (because it was handy on my shelf), did some calculations and found that the fateful decision should come (in my copy) on page 16. This is just before Polly takes hold of one of Uncle Andrew's magical rings and gets swooped off to the "wood between the worlds." I think that Digory, and not Poppy, is supposed to be the protagonist and he hasn't followed her quite yet, but pretty close.
|Wood Between The Worlds made of clay (by my kids)|
Anywhoo, it's interesting to examine pacing through the lens of this formula. I also looked at my WIP with this formula in mind and I think it'll help me plan out the ending.
This podcast episode also touches on the three main characters in a film: protagonist, antagonist (not always the bad guy!), and the relationship character (doesn't mean somebody the protagonist has a romantic relationship with). I won't go into it because I can't explain it better than they do. I encourage you to listen because, if you're like me, you'll look at character relationships in a new way.