A good person means well and does little harm to others. If they do some harm, they feel guilt and regret and try to make things right. Selfishness is kept to a minimum and tolerance is practiced.
I haven't thoroughly read every single one of the responses in here, but I have to say this one stood out, and strikes a chord with what I have in mind when I think of a 'good person'.
When I think of a 'good person', I don't have a list of characteristics in mind. All that comes to my mind is someone with a good, pure heart. I guess what I mean by that is open to your interpretation, but Gen's definition comes fairly close to it.
"...On and on and on and on he strode, far out over the sands, singing wildly to the sea, crying to greet the advent of the life that had cried to him." - James Joyce
And after adding them all up, this forum holds the following values in the highest regards...
Humor Independence/Responsibility Kindness/Compassion/Empathy Morality/Ethics/Fairness
Critical Thinking (The ability to question oneself and others)
Philosophy (The search for knowledge and truth)
Not having all those things does not necessarily make you a bad person, but for me, you at least need to try to have the bolded qualities to be a good person. As for the other qualities, you don't need them to be a good person and having them doesn't make you a good person, but they make you an interesting person.
I believe in good and evil and I think that a person becomes what they habitually do. Plus, your actions come from what is in your heart. If your actions are consistently selfish or malicious, chances are that you are a selfish or malicious person. Malice is evil and selfishness taken to extremes is evil.
“There are two novels that can change a bookish fourteen-year old’s life: The Lord of the Rings and Atlas Shrugged. One is a childish fantasy that often engenders a lifelong obsession with its unbelievable heroes, leading to an emotionally stunted, socially crippled adulthood, unable to deal with the real world. The other, of course, involves orcs.” ~ John Rogers