When we say "God", typicaly people mean a higher being or source of power beyond average means. Something that is completly distinguished from us in its characteristics of ability and awareness.
You can't. I think people who do this are simple and following a trend - just like those who say "I love impressionism" but couldn't tell you what it was or who did it. It's fashionable to be "spiritual" nowadays.
Are we talking about semantics now? I think beliefs are what they are. I believe I have a hand. I can feel it, when i sit on the hand it gets numb, I can bash it against the desk and feel the pain from the nerves inside of it. Similarly I can see a clock across my room, so I'm pretty sure its there. For now lets leave things at that and not delve into "the matrix philosophy" which I completely despise, that is, doubt of the senses.
Belief in something that is intangeble is no more radical than awarance of the obvious. After all, I have never been to Mount Everest. I hear its big, and I've seen pictures(representations) of it, heard testemonials(forgive the corney language), and I understand that I can go there and touch it. So I believe in it based on what I understand about it.
As far as evidence to the contrary goes(and I won't nitpick about "what evidence"), faith is, as the bible says, the evidence of things unseen. It is the internal drive which carries us past doubts and allows us to continue to believe in the illogical. This is not only applicable to a spiritual perspective, after all, many had to have faith to see things inconciveable at the time through, such as Orvile Wright, Charles Babbage, Thomas Eddison, etc. All created things that were rightly labeled preposterous before their time. Yet all came to pass.