It seems like a tired and overdone story, but each person's journey to reaching the conclusion that they are an atheist genuinely does color how they view the world and in what direction they will try and shape it. For that reason I believe a good starting point is to explain my journey and where I am at now.
I was raised in a religious family, but that was never the center of our lives. My mother spent her childhood roaming from protestant church to protestant church and, despite being a theist, doesn't hold one version of the dogma above any other. My father oftentimes seems like a reluctant Catholic. My grandmother takes things very seriously. I doubt my parents would have had a church wedding if she hadn't complained about it nonstop for months until they complied. If he had not had children I doubt my father would have spent his Sundays in church.
We went to mass every Sunday and church school was a must, but my parents never put "the fear" into my younger sister and me. My mother in particular encouraged us to question and was quite sure it was perfectly alright for us to disagree with what the church was teaching. Of course it was known to never air those out for my grandmother, but we were otherwise free to talk about our concerns.
As I moved through my teenage years I began looking into religion more and more. Each discovery chipped away at my faith, though I fiercely held onto the title of "Christian". I debated intensely on a Christian teen forum, going so far as to find myself banned for calling out the more unsavory beliefs and opinions.
I conceded belief after belief, from the divinity of Jesus to whether or not the bible is an accurate and useful tool in life, but I desperately wanted to cling to the idea of being a Christian. At first I was just a liberal Christian, then UU, just spiritual, and lastly admiring of the philosophy of Jesus. Christians blasted me for not "really" being Christian and the atheists I encountered mocked my crumbling faith.
By the age of 18 I finally admitted to myself that there was no point in calling myself a Christian anymore. I had discarded too many things to make the label worthwhile and the thought of being associated with some of the people who were in that category made me uncomfortable.
It took a while to really get involved in groups about atheism. Previous encounters left a bad taste in my mouth, so I wasn't in a hurry to expose myself like that again. Even now I don't find myself terribly active in groups. It's one thing to watch youtube videos or read blogposts and either agree or disagree while sitting alone in your apartment. It's a whole different monster to tackle when you put yourself out there for others to criticize, be it justified or not.
But I think those concerns are better left for another post.