A believable character is someone you know. Base a character on a friend or cast it as someone famous and the rest is easy. It helps to have acting behind you to form new characters.
Their responses to situations, their vulnarabilities of the moment - that which makes them human, or not.
A character must have depth and personality, I don't go for cardboard cut outs.
I think I may have touched on this earlier. I feel that a character is believable if he or she (or it!) can strike an emotional chord with the reader. The reader has to identify with something that the character feels or something that is part of that character as a person. These don't necessarily have to be good things - they can be bad elements, as well. But the expression of these traits is just as important as the traits themselves. A character whose dialogue or actions are completely inappropriate will ruin the story right away. It's a package: identifiable characteristics that are believably transmitted to the reader through speech and action. My characters generally start out based on someone I know or a composite of people I know - then they get embellished or switched around. This way, I have the basis for a believable character with room for imagination.
In order for a character to be believable, he/she must look, act, and sound like a real person.
if the character does not touch my feelings, s/he is not believable.
A character needs detail with awareness, to do things that real people do...real mistakes, real oversights, foibles and ticks, a human vulnerability. I create mine from paying attention to life around me, listening in on random conversations in restaurants, malls, and movie theaters, and composites of people I know and have known.
Over the years, I have devised a form that I fill in which describes my character's physical description, education, family history, religion, race, his or her likes and dislikes, dreams, values, faults, habits, and motivations.
It just tends to flow, and I biuld thecharachter around the story and the rhyme...
To me they must be plausible. Nothing annoys me more that a character doing something that would be out of the range of their expertise or they rely on coincidence to reach the conclusion.
My characters seem to develop themselves. I give them a name, I put them in a situation and they just seem to evolve. For instance I am writng a scree play with my son. The main character is a policeman. My son wants him to carry a gun, normal for a policeman, but when I tried to give it to him he refused to take it.
Honestly, every character is me. Learning to filter the many facets of one's own personality makes for undeniably real characters. We're all MPD, writer's just make it work for them. In each of us is bravery and cowardice, purity and licensiousness.
The writer has to be writing from a place of knowledge and comfort of the characters' and narrator's p.o.v.
To be believable, a character must have depth. You need ot know their favourite colour, what they think about the death penalty, they reaction to a crying child. even if those things never appear in the book, knowing those items comes across almost unconsiously.
Create the characters for storytelling with unique individual traits and stick with those traits, even through dialogue. Do not allow characters to meld together as one.
As a child I would sit and listen to people and watch them as they walked by. I still hear people when they speak, I still listen and watch them walk by. When you fall in love with people it is not hard to create from a world of pure joy and magic.