Depends, if it is with my friends I have known for a while then the topic is avoided. I am the only Atheist in my group of friends, the topic of religion came up once and it got pretty heated. We agreed to disagree.
If it is some one that I am getting to know. Then I will ask, I am interested in what people believe in, even if I don't believe in it myself.
But I don't start the religious discussion with the intention of starting a fight.