Story lines of your secondary/minor characters
Developing your protagonist’s story is relatively easy. After all, his or her storyline is the core of the story itself. However important it is not, on its own.
Even if readers don’t get a day-by-day account of your secondary/minor characters, as a writer it is important to know their timeline. The reader should be aware of the key events occurring in the life of your antagonist, the best friend of the character and so on. This way the reader doesn’t feel that the secondary characters show up a bit too conveniently and that their lives revolve in an unrealistic fashion around the protagonist.
Ask yourself, why the villain shows up only at the end of the book? If you don’t have a reason, there is a high chance that your reader will think it to be very contrived or convenient. Try to think about the life of the villain, his timeline, until you understand why he can’t or won’t make the move until the final chapters. Perhaps the antagonist is busy with another problem? Or maybe he needs to retrieve a weapon before attacking your protagonist.
The same principle holds true for the friends of you main character. If they are late for a meeting in a chapter – ask yourself why they’re late. It is not enough for them to be late so that the protagonist can have a confrontation with an antagonist. Perhaps the best friend is late because they had a fight with their mother or a flat tire.
Then, when a friend does show up to help your protagonist, think again, why they were at the right place at the right time. Did they have a hunch where to find the protagonist based on some information shared previously? Were they in the area on a personal errand?
Everything in your story should be plausible and even though your hero is the main character, the other characters around him or her should have their own lives, their own goals and stakes.
Speaking about goals, consider why the antagonist wants to hurt the protagonist. It is lazy to assume that the villain is simply bad. Perhaps he is out on revenge, or sees things different. Maybe he wants something that he can’t have unless the protagonist is out of the way. Remember in his own mind the antagonist believes he is the protagonist.
You can include the storylines of your secondary and minor characters in your chapter by chapter summaries or note them down in your individual character sheets to ensure that you keep track of them.