I believe that often people try to offer answers to that question that are too simple. It is always the obligation and goal of a Christian to be a Berean: to compare what is being taught to what is found in Scripture.
As soon as it was night, the brothers sent Paul and Silas away to Berea. On arriving there, they went to the Jewish synagogue. 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. Many of the Jews believed, as did also a number of prominent Greek women and many Greek men.
Thus, when I am presented with a teaching, my mind immediately goes into "scan and analyze" mode, not "open and receive" mode. Regardless of the source of the information, even if the message comes from a trusted and intimate brother or sister in the Lord, their words must be examined by the Word. Are they able to give contextual, rational Scripture references for what they're saying? Does their message line up with the whole counsel of God (what the rest of the Bible has to say on their subject)? Are there any red flags in my heart that the Holy Spirit is waving?
Granted, we cannot trust our feelings; anything we seem to discern from the Spirit must also be run by Scripture.
Let me give an example, using the Pearls' teachings, since they have figured in recent discussions. If you are a reader of this blog you already know that there are many things that the Pearls and I agree on. I've written several (ongoing) reviews of Debi Pearl's latest book and have discussed their ministry in a positive light here several times.
When I read their works, however, I don't blindly embrace everything they write. The Bible instructs the Christian to discern between what is of God and what isn't:
For everyone who lives on milk is unskilled in the word of righteousness, since he is a child. But solid food is for the mature, for those who have their powers of discernment trained by constant practice to distinguish good from evil.
Now, in the example below, please understand that I am not presenting this as something I regard as an evil teaching. Rather, it's a teaching I disagree with but which certainly would not divide me from a brother or sister in the Lord. That, too, is part of discernment: knowing what is good, what is evil, and what just might be neutral (something that is hard for a passionate person to countenance, I know!).
The Pearls believe that the KJV is God's Word in English, and that all other versions are per-versions (chortle chortle). Michael Pearl writes in an article titled New Age Bible Versions:
"Twenty-eight years ago I launched into a study of manuscript evidences. As a result, I came to believe that the King James Bible is the words of God, and nothing but the words of God, to English speaking people.
Do you believe that the book you call a Bible is the word of God? If it is not a King James Bible, then know that the translators and publishers of your “version” do not believe that your bible is the Bible, the Word of God."
Do I agree with this? No. That's another post, but no.
Can I read other writings of theirs, sorting out what I do and don't agree with, and keeping the wisdom while discarding what is not useful to me?
Yes. And that's what I am suggesting we do with all teachers we encounter. We must be committed to (Biblical) critical thinking just as we are committed to learning and embracing truth. No one person is going to get it all right, and we can't denounce an otherwise totally solid brother or sister because we disagree on a minor issue. Likewise, we must not put a "God-stamp" of approval on a teacher who is propogating heresies. We must be in the Word enough, and on our knees enough, to know the difference as the Holy Spirit makes it clear (which He will).
I think another issue comes into play here as well, though I think some will disagree with me. I believe that teachers who have proven themselves solid and whom we have come to trust individually as we've heard their teachings and seen their lives are worthy of our respect. I think this point is often lost in our quickness to denigrate what we don't like or to confuse the person with a teaching that isn't heresy but is not preferred by us.
1 Tim 5:1-2
Rebuke not an elder, but intreat him as a father; and the younger men as brethren; the elder women as mothers; the younger as sisters, with all purity.
(Note: Again, this does not mean his teaching is never questioned. It means he is honored and respected.)
1 Tim 5:19
Against an elder receive not an accusation, but before two or three witnesses.
1 Pet 5:5
You who are younger, be subject to the elders. Clothe yourselves, all of you, with humility toward one another, for "God opposes the proud but gives grace to the humble."
Teachers, says James, will be judged more strictly (3:1). Their words need to be examined, taken seriously, honored but not deified. Worshipping a man (as some people really do, I think!) is wrong, but so is demonizing a brother and elder. I think we can examine, approve and reject teachings without resorting to either.