Creating book characters can be a lot of fun, but there is a process. How you wield that process is really up to you as the author. Many authors create a character bible consisting of everything from physical attributes to personality analysis. Some do this before writing that first chapter. Don’t get me wrong, it’s always a good idea to know who your character is before you place them in your story. But you will not know everything about them when you start writing that first chapter.
There will be moments while you’re writing your story when ideas about your character will begin to germinate in your mind, thereby giving him/her more depth. That’s great! Go with that! Those are unplanned parts of the character’s personality. Now, that type of situation typically works out great. But there are times when that happens, and it can throw a monkey wrench into the situation. For example, years ago when I was in the middle of writing my first novel, I had one of my male characters do something out of character. And I’m talking WAY out of character. I sat there, stared at the screen, and said, “What do I do now? I like what I had him do?”
The easy way to fix this situation would have been to change his action and move on. The complex way to fix it was to go back to the beginning and change his whole character, moving forward to that point. So that is what I did. In the end I was happier with him, and the story was better off as a result.
Can you plan everything about your characters from the start? You can try, but be ready when that runaway moment comes that makes your story that much better.

