In chapter 15, Atticus goes to the jail to protect Tom from a problem. In this regard, I believe when Atticus sees problems, he anticipates them and tries to prevent them. This situation also shows that Atticus is an extremely brave man, he seemed to know that tough men were on their way to harass Tom Robinson.

I think this also shows that Atticus puts himself in a situation of potential harm for the sake of another. That is true sacrifice. Read the analysis of the attached enotes page. Go to chapter 15 for a good quote.

In To Kill a Mockingbird, Atticus Finch is unquestionably a character who represents an educated man in the true sense of the word.  For, he is able to step back from his selfish desires and perform noble, altruistic acts instead.  Because of his character, Miss Maudie tells the children that Atticus is the conscience of the town, doing what they could not do. When he is assigned the position of defender for Tom Robinson, his sister asks him if he cannot eschew the task; however, Atticus replies that he is obligated to fulfill the assignment if he would keep his children from acquiring the "disease of Macomb county."  In another instance, the nobility of his character is evidence when Atticus ignores the vitriolic insults of Mrs. DuBose, instructing Jem to read to her in retribution for destroying her camellias.  After Mrs. DuBose dies, Atticus explains to Jem that she has been addicted to morphine, but wanted to die without its dependency.  He tells Jem,

I wanted you to see something about her--I wanted you to see what real courage is, instead of getting the idea that courage is a man with a gun in his hand....She was the bravest person I know.

That Atticus is also brave and a man of principle is indicated in his acceptance of the position of defender to Tom Robinson.  For when his sister asks him if he could not have declined to be this defender, Atticus replies that he is obligated to fulfill the assignment if he would ensure that his children not contract "Maycomb's usual disease."  Later, when Alexandra worries about the stress that the trial has upon Atticus as the other members of the community make him do what they lack the courage to do, Miss Maudie wisely cautions her to be quiet, saying, "...We're paying the highest tribute we can pay a man.  We trust him to do right."

And, while Aunt Alexandra has the theatrics of her missionary teas, it is Atticus who is the veritable Christian. This charitableness of Atticus is demonstrated early in the novel when Atticus scolds Scout and tells her that one must "climb into [another's] and walk around in it" in order to really understand that person.  Similarly, he reprimands the children for taunting Boo Radley and invading his privacy which should be respected.

Atticus Finch is also humble.  He has been known as the best shot in town, but the children do not discover this attribute until Atticus must shoot a rabid dog one day.  Afterwards, Miss Maudie tells the children the reason Atticus has not boasted of his talent:  "People in their right minds never take pride in their talents." 

After the children are saved from Bob Ewell's attack, Atticus Finch, with humility, expresses his gratitude to Boo Radley:  "Thank you for my children."

Atticus Finch deals with problems with fortitude, charity, reasson, and love.  Always he is an example to his children, loving but firm in what he believes is the right thing to teach them.  With the community he is fair and objective.