When I was a teenager, I was an atheist. Religion always fascinated me, though, and so in my early twenties I started exploring alternative spiritualities such as Wicca, even joining a coven at one point. With Wicca you have all the gods in the world to choose from, so people interested in spirituality or religion but not really down with prescriptive monotheism could find something they liked.
I tried and failed to find spirituality during those days, continuing to retain my atheism. The biggest thing I took from it was meditation. I changed my life to be more reflective and introspective. Several years later I decided to revisit the religion question. I fell in with a spiritual crowd on a big web forum.
From there I discovered Dr. David Hawkins. He was unlike anyone I ever heard about or studied. There was a technique he adapted called muscle testing. I took to it like a duck to water. I eventually rejected “esoteric spirituality” but retained a more open-ended sort of inquiry. I kick around ideas about what more there might be out there but the understanding is that the focus should be on this world and this life.
I would classify myself as neither an atheist nor a theist. My perspective is too broad to be captured by either philosophical stance. One of the things I have learned and fully believe in is that everything is connected. I am comfortable interacting and having deep discussions with all manner of people, and can have very spiritual discussions with even atheists.
If you want to know how a person could go about building belief in a deity, I would suggest going to a Unitarian church, they have plenty of resources available for people that want to feel a deeper connection with their spiritual side.