To add to the excellent response above, I would add empathy. Remember Atticus's mantra - to crawl inside someone else's skin before judging them. Atticus consistently does this in all instances - it is why he has Jem read to Mrs. Dubose, it is why he does not get angry with Mr Ewell when he spits in his face, it is why he puts up with his sister's digs at his parenting skills and his decision to defend Tom, it is why he makes the deal with Scout so they can still read so her first grade teacher doesn't get angry at her. In doing this, Atticus always leads by example and follows through with his actions.
Another trait is that Atticus is honest. I think the best example of this when he believes Jem was responsible for Ewell's death. Atticus doesn't hesitate to begin planning the trial and what will happen. However, it is Tate who finally gets Atticus to believe that Jem did not do it.
Atticus is both a product of his time as well as ahead of his time. He does not crusade to change the prevailing racial and sexist bigotry of Maycomb, but in his personal dealings he is scrupulously fair and just. He has the ability to see things from the other person's point of view. This applies to his dealings with Bob Ewell just as much as it does to Calpurnia and Tom Robinson. Miss Maudie sums Atticus up when she tells Scout that Atticus is the same person whether he is in a court room or just going about his daily business. Integrity, a sense of justice and fairness, honesty and basic human decency are all traits that characterise Atticus Finch and have made him a benchmark in the legal profession to this day.
He has a lot of traits. Most of all which is calm, buisy, and decisive. U know?