@gememers: okay, first, “character development” means how the character develops in the story after the story begins. so, character development versus developing the character.
things to remember: at least in a naturalistic work of fiction, every person thinks of themselves as the main character of their own story. the lead character. the main character. even if they fawn on another character, even if they follow a cause, they think of themselves as the main character.
unimaginatively plotted stories—not that you have to come up with an unpredictable plot—have characters doing just the expected thing and especially having the other characters only exist in relationship to the protagonist. if you make the other characters multi-dimensional, the main character will also seem more real. how that works, I don’t really know. it works, though.
if you think, “why would X do that in that in that particular situation? I’d do some other thing…” go with it. have characters make the unpredictable choices.
also think that characters think differently. have that inform their actions and the way that they talk.
work out the absolute boundaries of the characters. what would break them, what would push them into drawing upon their strength. what would they, under no circumstances do, and what might they do if pushed and what would push them. (it would probably depend on a relationship they had with another person or with their nation, religion, etc.)
I don’t find the list method useful. you want to develop a character not list characteristics.
though it depends, it works best to have the story and characters work in concert, with each reinforcing the other.