How did you come to believe, or not believe, in God?

I’m going through some soul-searching about this, so I thought I’d ask for other people’s experiences.

For those of you who are atheists, how did you come to your beliefs?

Are there any former atheists here who would like to share their experiences?

Please, please, please, let’s keep it nice, non-judgmental and non-preachy. Thanks. :)