What: Separating what the character outwardly pursues (the want) from what they inwardly need (the need).
Why: The tension between them is the soul of drama, and the climax is the moment of choosing between the two.
How: Define your hero's outward goal, then the deeper need that opposes it, and let the plot force the choice.
Common mistake: A hero with a want but no opposing need, so the inner drama disappears.
Exercise: Write a paragraph defining your hero's want and need and how they conflict at the climax.