You define morality by what you believe is right. It is true that deas of morality have evolved over the centuries, but hopefully we are reaching a point when we can define morality, with or without religion. Two examples of former moral beliefs:
You can not. you can try, but you horribly contradict yourself. Without religion, you can not condemn others for doing "bad" because everyone is just doing what THEY believe is right. And we all have different ideas. You can not say we all have the right to believe whatever we want, because what if someone believes all blondes should die. Without religion, who is to say you can't believe that. Christians can, Mormons can, but atheists can not.