What are subplots and why do you need them? You have your story, you have your main conflict, all you need to do is get your character from point A to point B no? So what happens if you do that and the story is over without the main character having any adversity. Your story will fall flat and probably will be more on the boring side. So what do you do to spice things up? You create subplots. Mini stories on your main story that will give your character either the tools to defeat the villain or the emotional stress to grow up or change.
With the subplots, you can create new conflicts to show how the characters interact in different situations. Will they run? Will they have the courage to battle the obstacle? Maybe they do run. But because you are creating new conflicts maybe that character grows and in the end, he/she/it can find the strength to battle the antagonist. One thing to keep in mind when creating these new mini-stories is to remember to advance the main plot itself. Don’t write to writing. Make the character gain something or lose something to make the audience see who that person is. Maybe the story is going very fast and you need to slow things down.
What else can you put in your subplots? Maybe your stories are about zombies but you want to focus on how a person would do anything for the safety of his/her family. You create new moods. You show the character’s behavior and also you reveal what was your main purpose in writing your piece.
Andrew Walker’s Seven (Se7en) is about art. People tend to say it is about gore or how detectives deal with their day to day stress. The scenes open up when they show each crime scene. Also after “LUST”, the characters go to talk to a man that reveals the movie is about art. You get to get involved in the subplots of the story that when the climax comes up, the word used to build that scene is: “Complete the masterpiece”. And of course, it is well executed. But in the movie, the subplots are so well done that each one feels like a tiny build-up towards the end.
Now that you know a bit of subplot, make it fun. Make it grueling for the characters so they grow and learn. So they get stronger and wiser. Check for plot holes, advance your story so it looks like a build-up towards the climax. Reveal information needed for the characters to continue forward. Or set them up for failure so the characters question their motives. Speed the story or slow it down to change pace. And make sure your characters have all the tools before reaching to the final battle against evil… or whatever your story is about.