No, this is not a post on how to get yourself to meet your NaNoWriMo word count goals. This isn't about "get your cursor moving" motivation at all.
This is about motivation within the story--motivating the characters as well as the plot. First, a little background on what prompted this post.
I was reading (and generally enjoying) a pair of books from a particular series. The first red flag came when a side character was killed and I felt nothing. Maybe it happened too fast, maybe it was a failure to develop an emotional connection earlier ... or maybe it was because it "just kinda happened." Moving on, the MC executed an impressive string of "just doing things" for no clear reason other than to conveniently get herself in trouble. That's when I really started thinking about it and the failings of motivation.
Anyone who's tried to write a query letter has probably explored character motivation related to central conflict. What does the MC want and what stands in his/her way? My exploration has taken me from that macro level to the micro level of individual scenes and character actions or decisions. I've concluded that there are two types of motivation. I'm sure someone out there has more technical names for them, but this is how it's worked out in my mind.
This is what triggers a character's actions. Why does she do this? Why does he react that way? It stems from preceding events as well as the character's personality and values. The trick here is to make sure our characters act and react in realistic and consistent ways, keeping them imperfect yet still believably human. If a character's going to make an obviously poor choice, the reader should be able to buy into the reason. Show the doubts or the willful rebellion, whatever it is that drives the decision.
This is why an event/decision/development is worth including in the story. A few random details for flavor are fine, but anything more substantial should have a reason for happening. It may be the resolution of an earlier mini-conflict or the catalyst for something to happen later. In essence, it's what keeps individual scenes connected.
Both types are necessary, and different scenes will have a different balance of front- and back-end. I imagine few could be described as 50/50, but 5/95 (or 95/5) should be likewise rare. What happens when the balance is weighted too far to one side--or worse, when one side of the motivation is missing?
Back-End with No Front:
This dilemma inspires the "Well, that's convenient" reaction in readers and seems to be at the root of my instigating experience--the MC who "just does stuff." As authors, we know what we want to happen, so sometimes we force our characters to jump through hoops, just for the sake of making something work in the plot.
Front-End with No Back:
Scenes with this problem may come across as feeling random, tangential, or even indulgent. I suspect it occurs more when a writer is trying to pad the word count, or perhaps when the plot isn't yet fully formed. The characters do things that make sense given their personalities and prior events, but it doesn't really go anywhere. I'd say it's nothing to be too afraid of in a first draft if you're a fly-by-the-seat-of-your-pantser rather than a planner, but definitely something to watch out for in editing.
Neither Front Nor Back:
Sound the alarm and get thee a reality check, pronto! Characters are reacting inconsistently and randomly, and the story is going nowhere. At its most extreme, this isn't a story--it's words spewed onto a page. Might be okay for a free-write to play with dialogue or characterization, but once you're in story mode, these things need to be reined in ... at least to a degree.
So, let your characters be human (even if they aren't human, SF/F writers). People rarely do anything truly random. At the same time, be judicious in choosing which human moments to include in your story, and be mindful of why you've chosen them.