Last week I talked about when characters run amok and do something unexpected, and you're left trying to figure out what to about it. If it isn't something you thought of when you originally planned out your book, it may be difficult to figure out where this change can happen. How does it affect the rest of the story? Do you have to completely overhaul the whole book or can you just sneak it in?
If your characters are nice enough, maybe they'll make these random decisions ahead of time so that you don't have to completely change the events of the book. Or maybe it won't be such a life changing event and you can just sneak it in somewhere. The best possible scenario would be to figure it out before you even start writing. If you've got just an outline or even a rough idea in your head of what will happen in the story, it will be pretty easy (or at least not as hard) than having to completely change something you've already written.
Luckily my rogue character was nice enough to throw this curve ball at me before I even outlined the book. When I first thought of the moment when he reveals a secret to the MC, my initial reaction was, "So???" This was a character who was never meant to be important. If you've got an unimportant character suddenly trying to become important, it's going to seem strange. And no one is going to care.
I always had the rough outline in my head of what would happen in the second book. And this particular character was going to have two, maybe three lines. But apparently that wasn't good enough for him. The thing that really changed, though, was having this moment inspire a third book, where said character would be extremely important. But I thought, is anyone going to care? If he was basically a background character in the second book, how believable is it to upgrade him to love interest by the third?
The answer wasn't that hard to figure out. He can't be this cardboard cutout in the second book that I originally planned on. I need to figure out a way to make him more important so that the reader will actually care about him, and also find the third book believable. I don't want to shove him in the reader's face too much because that would drastically change the plot of the second book, but I think there are more subtle ways to sneak him in.
It's just really great that I'm figuring this out now instead of after writing the second book. I'd hate to have to go back and change everything. Imagine if the second book was already published! It would be impossible to change it. So sometimes your characters may do something that throws you off, but if they're nice enough, maybe they'll let you know while it's still early enough to change things.