on Fiction University:
A great character has more to them that just a few obvious traits.
Developing believable characters is one of the most important components of writing fiction. One technique for creating three-dimensional, consistent characters is to know them as well as you know yourself – even before you start writing.
If you struggle with creating characters, it may help to think of developing a character layer by layer. Here is one simple, 8-layer method for developing a realistic character.