Master the Possibilities
When you start a novel, the options are virtually limitless. A character can go in almost any direction. As the story progresses though, all of those options should fall away until the only option left is the conclusion. Think of your story as a tree. In the beginning, a tree is just a seed, and it can grow in many directions, both up and down. As you move along a tree though, you eliminate options. If you move up, you have left the roots behind. If you move past a branch, that branch is now behind you and can no longer be chosen. When you choose a branch, you eliminate everything but that branch. As you follow that branch along, you move by other branches until make another choice. At that point your choices are narrow. You are running out of branches until eventually you reach the end, where you have nowhere else to go but to embrace that final leaf or bud or whatever form your conclusion takes.
Decisions Define both Characters and Stories
The choices in a novel run along those same lines. Every word, every paragraph goes toward defining your characters, your plot and your themes. Each choice your characters make eliminates the other choices that could have been made. As each choice comes up, it further defines the character and it eliminates the choices that they could have made. The character might make dramatic changes as the story moves forward, but those changes must be the result of their earlier choices. Eventually, the character runs out of choices. They arrive at the ending knowing that it is now the only ending that remained possible.
As the Plot Progresses, Even the Same Decision is Different
Keep track of the choices that your characters make. In the beginning, your protagonist may be a high school graduate who must choose between college and work. If he chooses college, then he must choose a major. If he chooses a major, he has to choose from a specific set of classes. If he goes to the class he must take a seat. If he takes a seat between two people, he may choose to talk to one of them, none of them or both of them. If he talks to one of them, that person may turn out to be a friend or an enemy. If that person is a friend, they will go places together. If they spend too much time doing things other than classes, the student fails out of college.
At that point the student once again must choose, college or work, but he is not at the same point as he was in the beginning, even if he is making a similar choice. Getting back into college will be hard this time. He may have to choose a lesser school, foe example. If he goes to work it will be as a college dropout or perhaps as a part-time student who must hold a job as well. Either way, his choices revolve around college or work, because those are the branches of the tree that follows. If he fails at college again, the chances are very slim that he will have a third chance. Meanwhile, he has acquired a friend along the way, and that friend would not have appeared if he had made different choices.
Sometimes, Decisions are Made for You
Sometimes, in a novel, outside forces determine some of the branches. For example, his parents may have been paying for college, but then they lose a significant amount of money when the stock market crashes, and they can no longer afford to help him out. He must now make his choices based on the new situation. Be careful with outside forces though. It is usually better for a story if the characters’ own choices determine their fate as much as possible. The outside world may act to eliminate some options, but for the most part, rely on your characters to determine their paths; otherwise the conclusion will feel unearned.