Warning: none of this earth shaking revelation, just stuff I've been sorting out in my head.
You have probably read about character arc, if you've done any delving around the craft of writing at all, and you've also (I trust) stumbled upon the concept of milestones, or plot points, which are associated with screenplays as much (or more) than novels.
But how do the two overlap? You can have a good novel where not much happens and you can have a cracking story where the characters are simple as plasticine.
Character. I think it was Forster who came up with the concept of rounded and flat characters. I think we can define those two better. There is possibly three types of character, in fact.
The character who appears in the present, the character with a backstory and the third character type who changes during the story.
Let's label them something useful so I can refer to them.
The first type we meet and hear their voices, see what they look like, even smell them, note their idiosyncrasies, laugh at them or run from them or just buy a newspaper from them. They don’t change or have a backstory to motivate them, they just ARE. Dickens had hundreds of these little cameos, characters that spring out of the page and are gone, or reappear later fleetingly, just as alive but as comic as they are anything else. Let’s call them But they could be regulars in the cast too, a gang member with a set of characteristics and no backstory, say. Like Sleepy or Sneezy of the seven dwarves, defined by their names. In fact all the dwarves have no real backstory, and unless you define Grumpy’s conversion as some sort of character arcthey don’t change much either. Let’s call these people the CAST, because they are more than extras but they are not PLAYERS.
The PLAYERS have a backstory. One we find out. Motivation. A cruel childhood, or bitter divorce. Abandonment issues. Whatever you want to invent. We find out what makes them tick. They might even get some sort of resolution by learning to live with who they are. In a weak rom-com the we might have two players as the stars and there is minimal change, just resolution of a misunderstanding.
What separates a good rom-com from a bad rom-com (script-wise at least) is that in a good one the external misunderstanding or problem is resolved only when the hero and heroine overcome the character flaws that kept them apart. This is true of all genres (and non-genres) too. This is the HERO (or the HEROINE, but please take that as read). The Hero has a flaw that needs resolving, and it is always resolved by self-sacrifice - unless of course the flaw is that he/she never thinks of themselves and must say NO and be a bit selfish, but let’s not overcomplicate this).
So we have the CAST, PLAYERS and HEROES.
Let’s concentrate on the opening of a story and talk a bit of screenplay language.
What happens in a story is we have an “inciting incident” and the first plot point. From a character point of view these are not the same thing.
Well in simple terms we are saying SOMETHING HAPPENS and then SOMEBODY REACTS.
The “something happens” can be anything at all from zombie invasion, death of a pet or just a low mark in a test. It triggers the story in that it changes the status quo.
But what is important, and where character comes in, is how the character reacts. What he/she does next. Whatever the decision it has consequences, they can’t turn back (or won’t), it is uniquely their decision and it a character reaction to a plot point.