You know which books don't have subplots? The ones that never make it past the midlist (with some really weird exceptions).
I've developed a not-recommended habit of picking up the early works of bestselling authors. Unless you are an author: Don't Do This. It will make you cry. I'm not sure most authors should do this, it might make you cry too, but there's something very educational in looking at a bestsellers work from twenty years ago and comparing it to what they have on the shelf today.
What I'm seeing in a lot of debut novels is a lack of subplots. The main characters are established, the minor characters are established, the goal is given, and ... that's it. There are no side quests, no jolting bumps in the road, maybe a few curve balls but never the mini-story that is the hallmark of the subplot.
The big red flag for this has become the Training Montage. An unknown or weak fighter joins the group/fleet/hero/vampire roller derby team and must be taught how to be awesome. In a bestseller this training happens while someone tries to stab the person in the back, or happened before the novel opened, or is summed up by, "After six weeks of intense training I felt drained, but I was able to keep up on the nine mile death march."
Another red flag is the fantasy favorite travelogue as the characters walk for six months to cross a continent.
Chapters and chapter and chapters of nothing happening. No conflict. No fights. No information gained that couldn't have been summed up in a matter of sentences. I know authors are trying not to Tell (evil, boos, hiss!) but showing is not an excuse to be lazy or boring. Never, ever be boring.
The main plot should never be neglected, but there are times where it will reach a natural low point. This is where the subplots become so essential. Something needs to happen while the characters walk from Point A to Point B. A new enemy appears, someone betrays something, a romance starts, there's a spy! Pick something!
Although, be wary because romances as a subplot are better woven into multiple subplots than left alone. Romance plots need a partner or they sound weird. That's just my opinion of course, and depends a lot on the genre, but I like a romance plot mixed with the other plots because it tends to come across as a naturally developing relationship rather than BAM! Eyes Across The Crowded Room It's LOVE!!!
Quick And Dirty Tips For Creating Subplots- Not everyone should love the hero.
- The more antagonists you have the more conflicts you create.
- Real life should happen to the characters, even if they are saving the world they have jobs and responsibilities.
- Give the character interests and friends outside of work.
- Multiple point of views aren't a bad thing if you know how to juggle them.
- It all needs to come together at the end.
- Not every antagonist needs to be vanquished at the end.
- - Give us more than one character to love-- (from Diantha)
-- Make each and every character count -- (from Diantha)
Have you got anything else to add?