According to Dwight V. Swain in Techniques of the Selling Writer, the story must have a focus character. All stories need characters. To draw the reader into the story, there needs to be one character the reader can focus on, to experience this character's emotions. How does one choose this character? Is this the character who first popped into your mind? This could be true but there needs to be more.
When writing romance and some stories of suspense I've found there can be two focus characters. Still, one of these seems to shine brighter than the other. Does your story call for the hero to be stage center? Could it be the villain? Or the heroine? Any of these can become the character the reader hopes will win.
Winning may be the key. Which character has the most to gain or the most to lose if the goal isn't reached? That is the question you have to answer.
In my own writing, except for my mystery stories told in first person, choosing the character can be difficult. For me, there is usually a dual focus character since many of my stories hold romance. But always one of these characters is a little stronger than the other. This is the character who has the most to lose if the goal isn't reached.
Often in my romances the focus character is looking for a family, someone to belong to and to be with. The other focus character usually starts out not wanting what the other character does. The story is based on how the characters come together. It's not about winning or losing for either but in forming a new union.
So when you start a story, decide on who your focus character will be and show their actions and reactions, their emotions so the reader can focus on this character and want to read the story to the end.