we won’t really know him, unless you let us inside.
You show the inner world of your character by telling the reader his thoughts, emotions, attitudes, fears, longings, neuroses, drives and compulsions. There are two kinds of thought your character has: (1) thoughts about events that have occurred and (2) peripheral thoughts.
The way you introduce your character sets the tone for the relationship introducing between the reader and said character. Before a reader can bond with him, he has to know some basic details, such as gender, age, level of sophistication in the world and key characteristics. Reader distance themselves from characters who begin an emotional response to something the reader hasn’t witnessed.
Omniscient is the all-knowing narration, mentioning what this or that character is thinking or feeling any time the author pleases. Characters are kept at an arm-length and equal. The reader finds it harder to identify with one character and to get involved. Thankfully we have many viewpoints to choose from. Readers can live the adventures along with the characters by hitching a ride on their shoulder or even from within their minds.
Martha Beck (life coach) wrote a book (The Four Day Win, 2007) and dug into the world of science and looked into data from social sciences to discover the process people go through when changing their lives. She uncovered the Transtheoretical Mode of Change, which is pretty damn handy when writing a book, to make sure you have believable character transformation.