Like in life, our characters should be 3D. Heroes and villans should be multi dimensional, it makes it necessary for us to find out what those dimensions are. These three realms stand alone as unique, yet they always overlap.
1st dimension of character – surface traits, quirks and habits. This is the exterior of our character, their personality. What we see and apply meaning to. This could be the truth or it could be a mask, but without another dimension (unless its a peripheral character) the reader will never know. We don’t need to delve deep into peripheral characters, but saying that giving them stereotypical quirks can easily cliche your character. Being quirky for the sake of it in storytelling is a no go. Standard quirks make a 1 dimensional character.
2nd dimension of character – backstory and inner demons. This is the inner landscape of the character. This is about the path they have been on, the scars they have picked up on the way; dreams, memories, resentments, fears, habits, weaknesses, inclinations that all connect to give an appearance of what they seem to be. The inner landscape let the reader connect and should incite empathy. The more the reader feels for a character the greater it will be.
3rd dimension of character – action, behavior and world view. A hero takes a stand, takes risks, makes decisions, dives in and executes. A villain rationalizes behavior and is insensitive to, or refuses to accept responsibility for, the associated costs and violations of accepted social standards. The character is defined by a moral sense, or lack of. You may been angry enough to punch someones lights out in your life time. You made the moral decision not to, and that defines yo; but then imagine if you did. Its the same backstory but a different decision, now a different dimension of the character manifests. Using this, the first 2 dimensions may or may not indicate the 3rd, but this is a tool that the author should use to layer up a deep character.