For a good portion of my life as a Christian, I have held a range of beliefs that I have no official name for. Of course, since I believe in the Sufficiency of Scripture, I don't necessarily believe these names are important. Christians went centuries without calling the Doctrine of the Trinity "the Doctrine of the Trinity", so fancy names for other doctrines are just not important to me. Nevertheless, over the centuries, Biblical concepts have been "smartened up" a bit. Words and terms not used in Scripture are used to describe concepts presented by Scripture. Unfortunately, the same is true for false doctrines, and even entire denominations. The question we must ask, then, is how do we judge these things?
For me, the answer is study the Scriptures first, judge man made philosophies later. For me, the most recent example is Molinism. I have not studied Molinism in any depth at all, having only recently discovered the term. From the three hours of video produced by a Molinist I've seen, however, it does seem Molinism fits in with what I already believe. Due to a lack of study, I simply cannot identify as a Molinist just yet, but in the future, I very well may. But as I said, the reason for that would be that Molinism is a name given to a set of beliefs I already held. It would not be the case that I would suddenly interpret the Bible in light of Molinism.
[Post publication note: I have since studied, and accepted Molinism, but have decided to leave the above paragraph near enough unedited, as the point still stands.]
By contrast, I find that Calvinists interpret the Bible in light of Calvinism all the time. Sometimes, this is as simple as reinterpreting words that need not be reinterpreted. For example, the word "world" does not always mean the entire human race. However, there is no justification to interpret it in any other way in either John 3:16, nor in 1 John 2:2. Furthermore, there is no context in which "world" could apply to all Christians, or even all Calvinists, without also encompassing the entire human race. Only in light of Calvinism can such an interpretation be reached. Other times, Calvinists go as far as to literally add words to Scripture, such as changing 1 Timothy 2:4 to read "all kinds of men" when in reality it says "all men", and the context of the passage bears that out.
A good judge of doctrine is which attitude you have to take in order to sustain it. If you can let Scripture stand on its own, that is a good indication that your doctrine is good. Sola Fide (the belief that we are saved by faith alone), for example, can be defended simply by citing Ephesians 2:8-10. Those who reject Sola Fide must add to, remove from, twist, or even completely ignore this verse, whereas those who believe Sola Fide need only cite it, highlighting and expounding upon parts of it only if necessary. Similarly, Creationism can be defended by simply reading Genesis 1-11. It is so explicit that those who doubt it are invariably forced to claim Genesis is not supposed to be taken literally, because it's what Scripture literally says. Their arguments for this are ridiculously convoluted, and often atheistic. The aforementioned Doctrine of the Trinity can be defended with any selection of just 4 verses: One saying there is one God, and one identifying each distinct person of the Trinity as being that one God.
Although it is possible, and sometimes even necessary to add increasingly complex arguments to the defence of sound doctrine, a sign of good doctrine is that it needs minimal extra defence. By contrast, false doctrines cannot be as easily defended. An excellent example of this is Purgatory. Theoretically speaking, Purgatory can be as easily refuted with Scripture as a good doctrine can be defended. For example, 2 Corinthians 5:6-8 tells us "Therefore we are always confident, knowing that, whilst we are at home in the body, we are absent from the Lord: (For we walk by faith, not by sight:) We are confident, I say, and willing rather to be absent from the body, and to be present with the Lord."
But though Purgatory can be refuted by Scripture, it is often more profitable to make those who believe in it justify their belief with Scripture. This is an arduous task. Purgatory is not a belief that comes from Scripture. Rather, it is a belief that the Catholic Church jolly rogered from pagans. Even 2 Maccabees 12:39-45 is insufficient to prove that the Jews believed in a concept of Purgatory during the 400 Silent Years. Finding it in actual Scripture is a nightmare. Unless, of course, you are willing to read it in.
Just as this test can be applied to individual doctrines, it can as easily be applied to denominations. As a general rule, my advice is to just avoid denominations all together. Paul says to avoid divisions (1 Corinthians 1:10), and so personally, I refuse to play the denomination game. Nevertheless, denominations do exist, and the majority of the Church is inclined to choose one. Thus, if you are seeking one, or indeed if you are already in one and want to test it, test it against the word of God. If your Church faithfully exegetes Scripture, seeking not to follow man made traditions, but rather form its traditions on the basis of Holy Writ, in the manner described in this article, you're all good.
However, many denominations do it the other way around. Rather than studying Scripture and using it to form traditions, they form traditions, and insist that Scripture is to be interpreted in light of those. This leads to extrabiblical, unbiblical, and even anti-biblical beliefs and practices that must be defended by adding to, removing from, or twisting Scripture. In this case, the wise thing to do is to immediately abandon the false denomination, turning instead to God's eternal word.
All of this comes down to one simple concept: Exegesis. Exegesis is the practice of studying a text with the intent to decipher its meaning. Technically, you are (or at least should be) doing exegesis right now, reading my words, and trying to understand them. This is contrasted with eisegesis, the practice of forming a conclusion, and applying it to the text retroactively. It doesn't take a degree in literature to know why this is bad practice when applied to any text. When it comes to Scripture, it is as dangerous as renting out your tongue to Satan. Therefore, practice eisegesis on a daily basis (Acts 17:11), testing all things and holding on to that which is good (1 Thessalonians 5:21). Anything else is guaranteed to lead you into error.