A few years ago, I wrote articles under the name AuntieWIP. Most of the time, I asked questions and had others in my chapter give the answers. Other times, I wouldn't receive any answers, so I would give the answers myself after some research. The links for my research have pretty much gone bye-bye, but I left the ones that are still valid at the bottom.
There are three types of subplots: 1) connected, 2) comparable, and 3) conscience.
This one is the most obvious and, of course, the most used. It’s where a writer’s main plot has a smaller plot(s) that hints at or provides momentum or information for the main plot. This will give the main plot a three-dimensional feel and provide your characters with depth. Often used in larger book formats where you have more room for your characters to grow and show backstory.
A good example is in Debra Webb’s STRIKING DISTANCE. You have Tasha North tracking down an assassin to save the head of the Colby Agency. At first, you have no idea of the connection between the assassin and a main character, but as the plot moves along several subplots reveals their connection. The author subtly provides hints until the connection is revealed. So as not to reveal the twist, read the book and see how well crafted the subplots are entwined into the story. In this case, the subplot becomes fundamentally connected to the main plot.
This can be used for effect, but an author needs to be very careful. It can also become more of a fill, making a manuscript longer, and bore the reader to death. You take two plots, either of the same importance or one of more importance and written parallel of each other.
Sorry, it has been years since Auntie has read a book like this, though there are probably many excellent ones. The best example would be the movie LOVE ACTUALLY. A wonderful romantic comedy. The only connection the four stories had was that they were about love. The stories were presented in parallel of each other, but of different types of love.
All authors would like to use this more, but we have to be careful in popular fiction to not preach or push our particular causes on those that just want a good read -- a delightful escapism. We’ve all read books that tell us a moral behind the story or makes us think about how we treat the environment or our fellow humans. If you’re subtle with it, it can give a story flavor.
The one that comes to mind first is Linda Howard’s CRY NO MORE. Some of you are saying, “What? That didn’t have anything related to public awareness.” Linda doesn’t preach or thrust her views at you. It’s all woven into the storyline. You have mention of the Amber Alert and adoption practices that help but at times can hurt needy want-to-be-parents. None of the information provided in her book dragged down the main plot or made you feel like it’s all your fault. They actually solidified the story further.
For more information on subplots, check out the following:
Writing the Breakout Novel, by Donald Maass