I get caught up in what makes a character tick: their private wants, the secret fear they won’t admit even to themselves, and the small daily choices that reveal who they are. To me the single most important thing in character development is a believable inner life — not just a list of traits, but a root desire and a corresponding need that pulls them through scenes. If a character doesn’t have an internal compass that drives decisions, plot events will feel like puppeteering. Think about Walter White in 'Breaking Bad' or the shifting motives of the protagonist in 'The Last of Us' — their choices feel earned because their inner logic is visible and consistent even when they do terrible things.
Beyond that internal core, contradictions spice a character into someone memorable: a brave person who trembles alone, a moralist who secretly envies liars. I like to sketch a want-versus-need map: what they say they want, what they actually need to grow, and the lies they tell themselves. Then throw realistic obstacles and irreversible consequences at them. Relationships amplify development too — a character rarely grows in isolation. Watching how someone treats a friend versus an enemy reveals layers. In my own writing experiments I’ve found the most satisfying arcs come from choices that ripple outward, affecting others, forcing change. That kind of echo is what makes a character linger in your head long after the story ends, and that’s the kind of character I chase when I read or write.