You can have a great plot, but if your character is boring (or worse, annoying) readers are going to drop your books faster than kids are bolting out of their last class before summer.
Luckily, you only need to know 3 things to have an emotionally real character and the basis for a compelling story.
1. Emotional need
Maslow created a chart of the hierarchy of needs that every person goes through. Your more basic needs must be at least partially met before you can focus on the next needs. Throughout our lives we all move up and down the hierarchy as our situations change.
Survival: Has a rival spy blown your heroine’s cover? Is a crazy ex on your hero’s trail? Has the harsh winter made it difficult to find food?
Security: Is there a war or government instability? Is your hero homeless after his business when bankrupt from a corrupt partner? Is inflation eating up your heroine’s dream of saving up for a degree?
Belonging and Love: Is it super tough to make friends after moving to this small town? Is there an absent parent in your hero’s life? Does holding her friend’s babies make your heroine tear up a bit?
Self-esteem: Does your heroine need to know she can make it in the big City? Has your hero left a shady line of work, and is trying to redeem himself? Has a critical parent made your heroine sure she could never manage as a single mom?
Self-actualization: Has your marketing executive been suppressing her artistic soul? Does your hero need answers to spiritual questions before he can move on? What dreams are your character harboring? If your character had a midlife crisis, what would he change?
2. Goal
Every character creates an external goal that they think will fulfill their emotional need. You may have come up with the goal first, and now need to figure out the emotional need. Say your hero is at the Regency ball to meet a wife. Does he need a dowry which will keep him from the poorhouse (Security), a co-parent who can fill his responsibilities towards his niece (Self-esteem) or is the courtship all a smokescreen so that he can meet with revolutionaries that support a cause he believes in (Self-actualization)? Even in a romance, it is best if your main characters are not both looking for love. This makes it easier to sustain the conflict.
3. Flaw or Conflict
A flaw is an internal reason that the character won’t reach their goal. It doesn’t need to make them a bad person. In “The Sound of Music” Maria is a orphan who longs for a sense of belonging and decides to join the nunnery. Her flaw is quite mild; she is too lively and free-spirited to fit in with the other nuns. She eventually finds that sense of belonging with the Trapp family.
A conflict is an external reason that the character’s goal cannot be reached without some serious compromises.
4. Resolution
Resolution does not require "beating" the conflict. As long as the character gets his emotional need meet it is a satisfying ending. A character could grow to overcome his flaw, or realize that the goal won't give him what he needs and focuses his energy on something satisfying. Readers enjoy surprise resolutions.