Acts 17:11 says that "Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true." We should come to God's Word with "great eagerness." If we're more eager to watch a sitcom or the evening news than to read God's Word, inevitably our worldview will be more influenced by sitcoms and the evening news than by God.
We should "search" the Scriptures—we must probe deeply, not just skim the surface and quote verses out of context which back up our worldview. We must search the Scriptures, not simply always accept what others say about the Scriptures. The Bible should always be my primary source, and all other sources secondary. If I let secondary sources shape my worldview, I will not have a biblical worldview. I need a worldview informed by and corrected by God's Word. We need to see culture in light of God's Word, not see God's Word in light of culture. Our conclusion may or may not be politically correct (that changes with cultural winds), but we shouldn't care—what it should always be is biblically correct.
We should "search the Scriptures daily." Many other sources of input come at us daily—the media and the opinions of professors, family, and coworkers. If we study the Bible only partially and occasionally, it will shape our worldview only partially and occasionally. Our worldview will be determined by whatever we choose to expose our minds to. Unless I establish a strong biblical grid, a scriptural filter with which to screen and interpret the world, I'll end up being worldly in my thinking.
The Bereans searched the Scriptures daily "to see if what Paul said was true." Now, if ever in human history you were going to assume that another person's words were true, if you were ever going to take someone's word for it, not finding it necessary to double-check against the Scriptures, surely it would be with the apostle Paul. Yet the Bereans were commended for carefully scrutinizing Paul's words in light of Scripture. This reminds us that we should hold up under the scrutiny of the Scriptures not only the suspicious claims of an ungodly culture, but the well-intentioned words of godly parents and godly Christian leaders. If Paul's words needed to fall under the judgment of God's Word, so do all of ours.
Notice what happens here. Instead of God's Word being one more influence on us, God intends it to be authoritative over all other influences. It is not simply that I watch Seinfeld and read Time, the newspaper, Stephen King and Hemingway, and also get some input from the Bible. No—God intends that I read the Bible very differently than I read these others. I read it not simply as one more source of input, but as the Source and the authoritative standard by which I judge all other input.
Now, if I'm immersed in God's Word and biblically based literature, then and only then am I able to discern from the newspaper and Time and Hemingway and movies what values are being communicated and whether or not those values are true. Scripture becomes my grid, my moral filter by which I judge all other claims to truth. I can now pick and choose what is right based on my knowledge of God's Word.
But If I do not spend sufficient time in Scripture, or if I fail to realize the essential authoritative difference of Scripture and all else, or if I interpret Scripture in light of Seinfeld or Hemingway or Gladiator, then I will be led astray. If I am biblically grounded I can read the Book of Mormon and a book by the Dalai Lama and evaluate it appropriately. If I'm not, by reading such things I run the risk of believing untruths and being sucked into anti-Christian heresy.
This is why so many Christian young people "lose their faith" in both secular and Christian colleges. Being insufficiently trained in the Scriptures, they fail to screen out what their professors and textbooks and peers are saying (and how they are living). They absorb and end up adopting from the college a false worldview, usually a specifically anti-Christian worldview. Some reject their faith entirely and seldom come back to church, but many more become nominal Christians who have adopted a worldview that overshadows and undermines their faith—even if they remain church-goers.
It all comes down to this: is the Bible my authority, and how much time am I investing into knowing the Bible, so that I can interpret everything else in its light? Or am I giving my mind unfiltered access to all else, which will then dim the light of Scripture and cause me to be undiscerning and embrace that which is contrary to God's truth?
To be a biblical Christian, I must not simply affirm the inspiration of God's Word (that is necessary, but not sufficient). I must consciously critique everything else in light of Scripture (otherwise all else will unconsciously conform my mind to the world, the flesh and the devil). I must make a conscious effort to evaluate all my beliefs and my lifestyle preferences in the light of God's Word.
I must commit myself to making an examination, no matter how painful, of all my dearly-held beliefs (e.g. a loving God cannot send people to an eternal hell). And whenever they do not stand up to Scripture, I must abandon those beliefs. If I do not, then despite whatever I may profess to the contrary, my true authority is not the Bible, but my background, upbringing, peer group, the media, and schools that have influenced me. In short, I make myself and my culture (the flesh and the world) my authority.