In a marvelous book called, "The Complete Hanbook of Novel Writing," by Meg Leder, Jack Heffron, and the editors of Writer's Digest, Stephanie Kay Bendelis is quoted as saying:
"The difference between a good story and a great one is often the depth to which the author examines the characters who people the pages. Beginning writers are sometimes bewildered when they are told their characters need more development or that they haven't really allowed the reader to 'know' these people. In my teaching I have discovered that a good way to make sure your characters are fully developed is to think of them as four-dimensional persons."
This is very good advice. I have heard so many times that it is better not to create flat, one dimensional characters, all good--- no flaws, or even all bad--- with no redeeming qualities.