You may also be the type of writer who does better writing the story first and applying structure later.
As Z0Marley mentioned, sometimes this does result in massive edits. But I've found this system still works better for me than filling out beat sheets ahead of time. When I outline too stringently, my characters end up feeling like cardboard cutouts walking through the plot to get to the next necessary scene or plot point, rather than driving the plot through in-character decisions.
I do, however, tend to define a few key plot points first, then allow myself time to wander a bit between them. Later I'll get nitty-gritty with looking at the structure for weak spots and maybe doing a little rearranging, but in the first draft I need room to explore various rabbit trails created by my characters. (And yep, sometimes that means chopping out scenes or subplots later, or adding in new ones.)
The key things I do suss out ahead of time are:
- Inciting incident ("Call to adventure")
- First Plot Point (When the protagonist can't go back, or the "Crossing the Threshold". Later on, I'll look at where this falls and try to place it around 20-25% of the way through, but I don't stress about that in the first draft)
- Midpoint Turn (This is the big shift about halfway through or so. New information comes to light that changes the protagonist's expectations and mission, or the villain suddenly changes the stakes, etc)
- Darkest Moment (The "everything seems lost" point, where you wonder how the protagonist is possibly going to pull this off)
- Climax (The big finale. The final battle or confrontation, everything comes to a head.)
- Resolution/Denouement (The cool-down, easing the reader out of the story, what happens after the action of the climax.)
If I'm stuck on one of the plot points, I think about the key conflict of the story. What is the central driving conflict of the book? This would usually be the "stakes" part of the query letter, if I were writing one.
There are other points and scenes that fall between those listed if you get into detailed structure and beat sheets, but I finesse those later. In the first draft, I just focus on hitting these elements. In draft 2, that's when I'll go through and assess the acts and massage it until it works.
Everyone has their own process and this one may not work for you, but just listing mine in case it helps.