It’s often said that there are two styles of writing a book – ‘plotters’ and ‘pantsers’. Or, per GRRM:
The architects plan everything ahead of time, like an architect building a house. They know how many rooms are going to be in the house, what kind of roof they’re going to have, where the wires are going to run, what kind of plumbing there’s going to be. They have the whole thing designed and blueprinted out before they even nail the first board up. The gardeners dig a hole, drop in a seed and water it. They kind of know what seed it is, they know if planted a fantasy seed or mystery seed or whatever. But as the plant comes up and they water it, they don’t know how many branches it’s going to have, they find out as it grows.
In practice there’s going to be a bit of both, but I’ve noticed that a lot of the practical advice out there is aimed for heavy plotting. So, here are some points on how I give myself structure while leaning largely to a ‘gardening’ approach. If you’ve tried strict plotting and found it restrictive, but totally going by the seat of your pants would leave you lost, this might help you find your own process.
You’ve got some ideas milling around. Sit with them for a bit and figure out which parts can fit together for you to take further, and which you’re going to drop for now. Which still interest you a week or two later? You want to have something you think you can work with over a few hundred pages, but also not overdo it. One cohesive set is better than a jumble of good ideas which differ in style.
Worldbuilding, setting, character
In itself these are big topics! As it comes to plantsing, what you’re doing here is giving yourself a foundation to write the opening of the story and get some thoughts on where it can go. For example, I’ll start a map as an empty square with the first area noted somewhere, adding other places and geographical features as I mention them and characters move around during the writing. (This map is never fancy, just so I don’t get lost and screw up directions.)
Not knowing everything that will happen at the outset means you’ll be adding new characters, aspects to the setting, and points of worldbuilding as they occur to you and play their roles in the story. These have to fit with what you’ve already got. Keep notes, so later on you can make it seem they were always there from the start.
Once you have that foundation, you can form loose ideas on the plot. This might be very brief notes on potential endings and some major/interesting events along the way. Leave room to add, remove, and change the order of them as you actually write.
The overarching structure isn’t a concern yet. You’re just getting a sense of the first chapters, and a rough direction to head in from there, such as a climax for the first quarter or so. This will give you enough to get started.
You knew a reasonable amount about the world and the characters you started with, but the first chapter let you see this in action. As you become familiar with these people and the circumstances which shape them, the logic of the world itself and the motivations of the characters will take on their own inertia. In response to given circumstances, a given character will want to take certain actions.
Some of the checkpoints you thought up earlier won’t end up fitting in, while others will present themselves. Your task is to guide the characters into a natural sequence of events, finding a harmony between ‘what would they do?’ and ‘what would be good fiction?’. Create circumstances which your characters will respond to in such a way that it leads them into the next circumstances.
Now you can consider structure as you go: keep an eye out for pacing, so that each quarter or so of the novel can have a balance of action and reflection. It’s helpful to keep brief notes on what happens in each chapter, so you have an overview of the plot to check as you go, and to use when editing and writing the synopsis.
Bear your unfired Chekhov’s guns and loose ends in mind. Did you set something up, start a subplot? If you’re ever lacking a place to go, you could draw on those.
You’ll reach a point where you know exactly what will happen in the ending and how to get there. It’s easy from there. Little things to watch for are letting the pace get more hectic than is actually good because you’re rushing to an exciting scene, and not having enough after the climax to let things breathe and tie up loose ends.
Editing is another big topic in its own right. Likely considerations for a plantsed novel include situations where you added something on the fly and haven’t yet integrated it back from the beginning.
For example, you could go back and foreshadow events. Or if you came up with a plot-critical bit of worldbuilding in chapter 32, did you introduce it with an exposition dump to get it out and keep writing? Now you can refine that. Is there a more natural way to convey it, and is it missing from earlier scenes in retrospect?
Hopefully this gives you some ideas on how to approach a novel with a loose, lightweight approach to planning. Good luck!