I am no different than anyone else in this regard. My experiences and exposures, reactions to and ruminations upon life before the Bible was in the picture color the picture of God painted after I encountered him in the scriptures. For instance, I can remember, long before I was saved, walking down my street as a twelve year old on a sunny, breezy day, when something about the color and shape and way the leaves were fluttering on a maple tree struck me with the intense conviction that there had to be an intelligent, creator God. Prior to that, I didn't think there was one, but regardless, it was not the Bible that informed that new supposition.
That experience led me to reach out to God, to attempt the occasional talk with him, even though reading the Bible was the furthest thing from my mind. I would ask the "God out there" on those occasions about things, and I took the sudden inspirations that followed in my mind as responses from him. Sometimes, the inspirations came apart from any question on my part. I believed I was learning about God from God, even though I was fifteen before I understood who Jesus truly was (that's another story), and 19 before I started reading the Bible in any serious measure.
Sadly, it was actually some time from the moment I knew who Jesus was until I was willing to drop it all and follow him (a bit over 5 years). In my very first days of actually following Jesus, I had an encounter with him in my bedroom that left an impression on me that I'm still under. My experiences, before and after, have left me with with some presuppositions concerning God that (even though these convictions existed before I began to study the Bible) have proven serviceable in the time since when I've been studying the Bible.
Let me share some with you...
We can personally interact with God. God speaks to us today, not just to folks a long time ago in a culture far, far away.
Jesus Christ is the only visible God we will ever see--God in the flesh. The Father and Spirit are incorporeal and never will be discernible through the auspices of electromagnetic radiation (though they may choose to affect the visual realm). Jesus is the only means of knowing God and to know him is to know God.
The Bible is the infallible Word of God, preserved to us inerrant by God's oversight. It was inspired by God, not created by men. If we want to know with confidence what God wants to do in our lives, the Bible is the only place to look.
Do you know what some of your presuppositions concerning God are? Have they proven serviceable or a hindrance in your journey with Christ?