There’s been a lot written online lately about the 3-act story structure model for scripts and why it works or should be avoided. See, for example, John Truby's article and comments on the UK's Raindance website.
Dividing a script (a play or screenplay) into three structural parts is about as natural as a person living out their life, regardless of length. Call the three parts whatever you want, but a good story always has 1) a “beginning” or “launch” or “set up” where the central character and his or her main need or want is introduced [ACT I]; a “middle” or “struggle” or “series of obstacles” that the central character confronts in an attempt to satisfy that need or want, setting up conflict and rising dramatic intensity [ACT II]; and an “end” or “resolution” or “solution” to the central character’s dilemma [ACT III].
Every successful story contains these three parts in some shape or form.
I think the trick is to not get too bogged down with all the other terminology that’s been invented by story analysts to get you from one part of the story to the next. Terms like plot points, reversals, inciting incidents, etc. are great tools to have in your toolbox and you should be familiar with how each of them functions, but they can also be sources of confusion (leaving you with your eyes crossed, your brain fagged, and your fingers frozen) and must be used with a great deal of flexibility when it comes to telling your central character’s unique story.
Keep in mind that all great stories--dramas and comedies and everything inbetween--rise out of the characters that populate them. In other words, your people should always drive your story and not the other way around. And this starts with a multi-faceted central figure we care about and his or her need/want that has to be somehow satisfied. A journey ensues triggered by this need that introduces other interesting personalities, including those who set up roadblocks and obstacles along the way. Your story’s plot points will naturally materialize if you’ve created wonderful and even unpredictable people who either are in support of or in opposition to your the central character dominant need.
So 1)set up the central character’s problem, 2)have him/her struggle to overcome the problem within the world of the story, and then 3)have him/her somehow solve it in either a positive or negative way. And how you work the development of scenes and their progression should largely be determined by this unique central figure and how he or she responds to the circumstances thrown in his or her path. Your people (if fully realized with hearts beating) will hand you the details.