I think when we say a teaching is "biblical" we mean more than simply, "it can be found in the Bible". It has a lot to do with the preacher's desire to show you his teaching is found in the scriptures, because he wants you to believe it is true.
Removing the preacher's intentions from the mix, it sounds like you want to know how to extract truth from the Bible without him? I'm not sure that is possible.
The Bible replaced the priesthood as the ultimate authority in the Church ever since the reformation. Priests who were absolutely corrupt taught many things that were contrary to the scriptures. The alternative was to trust the scriptures over the corrupt priests. This has led to many corrections that the protestant churches have made along the way.
But I do not believe the Bible was ever intended to be the sole authority. The scriptures themselves do not predict a time when they would become so. No, they speak of the authority of the Holy Spirit, and the authority of the men of God that He chooses to watch over us. Oh, and also the authority of the scriptures.
But what they do not say is how the one authority of the scriptures can work without the others. Scholars try to make this happen, but in the end they add their own opinions to it and establish doctrine based upon the wisdom God has (hopefully) given them. They direct us to the passages of scripture that they see fit.
As Charismatics, we look to the Holy Spirit to explain the scriptures to us. And many times, what we feel He says is different than what the tools of the scholars might come up with. So which one is the final authority? The scriptures as revealed by the Holy Spirit, or the scriptures as stated in the original language while taking into consideration cultural customs, hermaneutics, and all the other wonderful tools at the scholars' disposal?
I think when someone says that "My beliefs are biblical" they are usually speaking an untruth. Upon further examination, it turns out that their beliefs are in line with what a preacher has taught them, and simply sold to them as "biblical" doctrine.
More and more lay people are realizing this, and looking for the magic that their pastors use to determine which doctrines are biblical and which are not. What we are finding is that there is no legitimate system for determining this. Simply that doctrines are voted in by committee because that is what makes the most sense to those who want to do good and see the advancement of Christianity.
Instead of a "Bible only" foundation, I would personally like to see something more honest in how it's described. Like a three part foundation (built up from Jesus, the one true foundation of course), stating that the scriptures, the Holy Spirit, and those ministers that God promotes to watch over us are all invaluable parts to the whole. But I also acknowledge that something like this would take an act of God (and not just lil ol' me) to put into place.
