Here are a list of quotes from the book with a short explanation following each:
"I ceased to advertise my mother's race at the age of 12 or 13, when I began to suspect that by doing so I was ingratiating myself to whites."
Obama is discussing his growing understanding of racial divisions in this country. Although he is of mixed race, his appearance is African-American. Therefore, he begins in adolescent to feel that he must ally himself with this group and separate himself from whites.
"It remained necessary to prove which side you were on, to show your loyalty to the black masses, to strike out and name names."
This quote reinforces the pressure Obama was feeling to choose between races. With social pressure, there was a need to "pick a side" in the racial game.
"I never emulate white men and brown men whose fates didn't speak to my own. It was into my father's image, the black man, son of Africa, that I'd packed all the attributes I sought in myself, the attributes of Martin and Malcolm, Dubois and Mandela."
In this quote, we see Obama moving beyond his adolescent fears and perceptions. As an adult, he has learned that loyalty is not about the racial divide, but about character. He has also learned that role models should be chosen for their race, but rather for their personal characteristics.
Correction to sullymonster's answer. He/She meant "shouldn't be chosen" rather than "should be chosen.