I was raised Christian, though my family almost never went to church. When the Disney cartoon Hercules came out when I was very little, I believed in the Greek gods for a short time, but I don't know if that counts.
When I was about 11, I became a Deist because I started reading bits of the bible and it did not seem divinely inspired at all, but I still thought there had to be some kind of entity that created the universe.
At 14, I became an atheist because I couldn't find any reason to think that the world had any purpose in humanity or the laws of physics.
A few years after that, I discovered The Satanic Bible and needed to take some time to figure out what aspects of it were core to Satanism and what aspects were the author's opinions or just common Satanic opinions. Once I more or less answered that question for myself, I have considered myself a Satanist, though I only wear the title when it's convenient.
So today I consider myself an atheistic Satanist, but in most social situations I don't mention the Satanist part... though, in some I don't mention the atheist part.