Develop Plots and Subplots for Each Book
This is where it gets a bit tedious if it's a series. If it's a standalone, I just go back and develop the subplots and add them to the manuscript according to the timeline.
For a series, I have to go back and do Steps 1 - 10 for each book. The only difference is that I only do the character sheets for the characters who are POV characters in that book. I like to keep it to 2 to 3 protagonists and 1 to 2 antagonists in each book, and of course, the main protagonist will be a POV character in every book.
Needless to say, some adjustments usually need to be made. I try to choose characters for each book that have the most scenes. I also have to look at whether or not there are important scenes that only have one character. During this process, some scenes may be deleted if I decide they're not important enough to drive the story, or some of the POV characters in certain scenes might change.
If a character is labelled as a POV character in a scene, but I have not chosen them as a POV character for that book, I will have to switch POV characters. Also, if the POV character is the only character in the scene, and they don't play a prominent part in the book, I might have to consider deleting that scene or making it something they talk to another character about later in the story if it's important.
Once I decide on the POV characters for each book, the idea is to develop a separate storyline that begins and ends in each of the books, which may or may not have anything to do with the main storyline for the series. Most often, it will be one of the subplots that was left out of the main story, or it could be a story that hasn't even been thought of yet. Sometimes I might even pick another character as the main protagonist for that book if that character's story is important enough.
For instance, in my Shadow Stalker serial, my main protagonist, Auren, has a forbidden love affair with another character. While this has nothing to do with the main storyline for the series, it could work well as the main storyline for one of the books I'm writing in the novel series (I haven't gotten that far yet, so I'll let you know).
After I work through all 10 steps for each book, I add the scene titles to the timeline and label on the timeline where each book begins and ends. This is where it gets tricky again. If a scene from the main storyline falls within the timeline for a certain book, it needs to be moved to that book (if it's not there already). When that's all sorted, I add the new scenes to the manuscript according to the timeline.
This step takes a good deal of time, but if done right, it really makes the story flow more smoothly in the end. It also prevents each book from ending in inconvenient places and with plot holes. While the main storyline is ongoing, each book will still feel like its own entity. Cliffhangers are great, but I feel the cliffhangers should involve the main storyline for the series, not the main story for each book and the subplots. When the book ends, I want those stories to end as well.
It also saves a lot of time down the road because I don't end up writing full scenes or chapters that I have to delete later. Working out the kinks in the story before I write it just makes more sense.