The story is about the character whose fate is most important to the storyline. The main character, or the protagonist, is usually the one with the most to lose or the one in conflict with the antagonist. In most cases, the main character will also be the Point Of View (POV) character.
Multiple POV’s
If you’re writing a story with multiple POV’s then the character with the most at stake in each scene is often the best POV to write that scene from. You can of course slip in and out of the head of every character in the scene if you wish, but you risk confusing the reader and making it difficult for them to become attached to your characters.
Sidekick’s Story
The main character of the story doesn’t have to be the hero of the story. They can be the sidekick or an observer. And example of this is Watson in Sherlock Holmes. By using Watson as the POV character, the mystery is maintained longer and it gives Holmes a reason to explain how he solved the crime. The reader is in a similar position to Watson in that they are following along with Holmes, trying to discover what is happening and wanting to solve the mystery.
What Is At Stake?
Your main character must need or want something. Without a thwarted desire, conflict, an antagonist preventing them from attaining something or an unmet need, there is no story. If your character has nothing at stake, then the story isn’t about them. It doesn’t have to be end of the world, save someone’s life kind of stakes. It could be wanting a pay rise, struggling to reach a destination when everything seems to go wrong or trying to find a way to meet the person next door.
Hostile Takeover
You’re several thousand words into your story, maybe even ten thousand, and one of your minor characters keeps trying to steal the limelight. Instead of continuing to push that character to the side, think about what the story would be like from their POV. Or possibly from both the current main character and the secondary character’s POV. Does this secondary character have more to lose? Is their story more compelling? Are their wants more important than the main character’s? Try and figure out the reason why this character keeps trying to take over. This can help you decide if you’ve chosen the correct main character for the story.
Trouble Choosing Between Two?
Some stories belong to more than one character. An example of this is Romeo and Juliet. Both their stories are equally important and add to the story, driving us towards their tragic ending. The characters don’t have to have a common goal for the story to belong to both of them. It could be about opposing sides of a conflict.
Genre Expectations
Some genres focus on a particular type of character. Romance stories revolve around the characters that are falling in love and are usually told from the POV of one or both of those characters. Detective stories are usually told by the detective and revolve around the steps they take to solve the crime. But as in the case of Sherlock Homes, these expectations can be broken.