Subplots are crucial to any story. Everyone loves a good “ordinary Joe discovers only he can save the world so he fights against the Evil and then lives happily ever after” tale (or maybe not necessarily happily ever after, but you know what I mean).
The trouble is, if that’s all that was happening in the story, you’d be bored, right? All Joe would ever talk about is saving the world and vanquishing the Evil. Every scene. Every conversation. And the story would be over in a few chapters.
The thing is, Joe had a life before he had to save the world, and his life didn’t suddenly cease the moment his quest was laid upon him. His Mom is still dying from a rare disease that only the hermit in the mountains knows how to cure, and his best friend since childhood has just recently revealed she has feelings for him.
Now we’re talking. Or rather now, thankfully, Joe has some other stuff to talk about. And some people to actually talk to, as well.
Because his best friend, Isabel, insists that she travel with him because, left to his own devices, he’ll navigate himself off of a cliff. So he can’t just ignore the fact that she’s making eyes at him and treating him like they’ve been married for a decade. We also get a heartbreaking scene between him and his mother when he leaves, and a frustrating confrontation with the hermit who is supposed to be able to know how to cure Joe’s Mom. Not to mention the stranger who recruited him to save the world is impossible to get along with, and somehow Isabel starts to fall in love with him, instead of Joe.
The thing about real life is you’re never dealing with just one conflict. Our main plot might be to make it through our lives earning a decent living and being happy, but there’s a lot more to it than that. To give a story depth, or at least any story longer than 1000 words (it’s tough to develop sub plots in flash fiction, although it is do-able), there has to be more than one over-arching plot.
For me, one of the easiest ways to incorporate sub-plots is to add supporting characters. Every character has his or her own life outside of interaction with Joe, so each person has their own motivations and their own goals. Very often supporting character arcs make good subplots, or at the very least, their relationship with the protagonist does.
Really, though, the best way to incorporate subplots is to give the protagonist more than one conflict to juggle while attempting to save the world, whether it’s a love interest, the development of a sudden unexplained and uncontrollable power, or even a boss who isn’t being very understanding about missing work while on a quest to rid the world of evil.
Maybe in the sequel he can take revenge on his boss for firing him.