I confess, I almost never finish novels I don’t plan, but at the same time, writing without having a plan is wonderful. You find that you are just as surprised by each little thing as your reader is! So, because you’re not planning anything, here’s just a few tips to keep your writing going:
Know what’s going to happen next, just not what’s going to happen after that. By this I mean, write with intention. Know which direction it is going in and let what happens next be a surprise and decide from there where to keep going. This way you avoid stagnation and just getting stuck in one scene because you can’t think of what the characters would be or should be doing there.
Leave mysteries to unravel. When you’re writing leave hints and clues and other things to explore. If you mention that a character has a twin sister, that means that there’s a 95% chance that the sister will appear, when and where can be a surprise, but really, it’s the reader’s expectation and it’s considered a loose end if you don’t bring it in (for example, in Larsson’s The Millennium Trilogy, the author mentions that Salander has a twin sister who never appears even though she presumably had a similar, though slightly better up-bringing, it’s assumed now that Larsson would have included her in his originally intended sequels. Also, in season 1 of the TV series American Horror Story, the character Constance mentions her 4 imperfect children, but only 3 of her children are actually seen after that. So these are SUPER ANNOYING loose ends.)
Create a plot. It’s okay if the reader can’t recognize it, just so long as you can. Not all books have to have plots, but it helps a ton if the author has intention and direction. You don’t need to have it planned to have intention and direction. It’s like going for a hike and saying, I’m going to walk towards that mountain in the far distance, but it’s okay it I don’t actually get anywhere near it.
Write scenes, not a manuscript. This might not help everyone but if you are inspired to write something just can’t think of how it connects with the last scene, it’s okay to write it as an individual scene somewhere on a timeline and see how you can fit it in later. The more individual scenes you write, the easier it is to put them all together later on. It might just need some bridging and transitions depending on the story.
