Just when you think you have enough to juggle in keeping your protagonist and antagonist in conflict against each other from story start to story finish–here’s another aspect to consider. Adding subplots can lengthen your story, can develop characters, can add dimension, and can help you fill out an otherwise thin story.
The trick to effectively using subplots is to plan exactly where and when they’ll appear and conclude.
Tip #1: A subplot should never be equal to the main plotline.
You don’t want two parallel stories spanning the entire manuscript. Sooner or later every writer is tempted to attempt this, and it so seldom comes off. The problem is that you end up with a split focus, no clear protagonist, no clear antagonist, and no way to effectively end the story.
Tip #2: Limit the number of subplots to what you can handle.
Keep in mind that each subplot has its own smaller story arc with a protagonist, antagonist, and climax that will answer its story question. How many can you manage without forgetting or neglecting them? What is the intended length of your story? How many viewpoints do you need to convey the story fully?
If you are writing a short novel of, say, less than 75,000 words, you probably have room for only one subplot, possibly two, in addition to the main one.
If you are writing in a single viewpoint, then you may want to limit the subplot to the protagonist’s internal problem–the growth or arc of change the character will experience as a result of dealing with the central plot’s issues.
A longer book, with multiple points of view, has room to accommodate several subplots if you wish. Just keep each one at a different level of importance.
Tip #3: Stagger the placement of the subplots.
Subplots don’t enter the story at the very beginning, parallel the central plot, and end at the story’s climax. Instead, a very short subplot might open the story–if there’s a good reason to delay the introduction of the main story question. Such a small subplot might end by chapter three, for example. The opening of Dick Francis’s novel, ODDS AGAINST, deals with the protagonist being shot and having to recover, answer police questions, and visit a crime scene to identify the victim as the man who shot him. It’s only because the protagonist is injured that he’s willing to get involved in the central story.
On the other hand, a subplot might not appear until the book’s middle. Let’s say it’s a romantic subplot for Simon Spy, our protagonist. Maybe he’s waiting for the convoy of missiles to reach the terrorist camp. Rather than let the book sag, Simon’s dalliance with a local beauty turns far more serious than he expected, further complicating his mission. The resolution of this subplot may not be resolved until just after the story’s climax, as part of the poetic justice dealt out.
Writing Tip #4: Make the start and finish of a subplot count.
Writing strategy deals with how a writer chooses to intersect major and minor plotlines. Where will those intersections occur? You want to make sure they happen at key turning points. They should inject new life into a sagging story, create plot twists, prevent the story from becoming predictable, and maximize the reader’s entertainment.