When you are making sense of a passage, you will often have to evaluate several options. Perhaps two or three possibilities quickly emerge to make sense of a detail in the text. Maybe different commentators offer different explanations. If you take biblical study seriously then you will face this frequently. How can we evaluate the options and weigh the evidence in support of each?
This feels like a preacher’s concern. Of course, it should be. I suspect too many preachers don’t wrestle with their passage enough to notice different exegetical possibilities. But it should not be just a preacher’s concern. What about the people in your church? Where will they get a taste for really wrestling with the biblical text and coming to thought through and informed conclusions?
The approach I use is not a formula guaranteeing results. It is not spreadsheet-based with automatic formulae. It is a guideline that helps me weigh evidence. If I have level 1 evidence then it will generally be given more weight than level 2 or level 3 evidence. At the same time, if I have evidence at several different levels, it may outweigh evidence at a higher level. This is a guide, not a formula. I still need to subjectively do the weighing, even when the guide gives me an indication of the relative weight.
So from most valuable down to the least valuable:
Level 1. Syntactical Evidence – this is support for an interpretational option that is found within the passage’s own structure or grammar. This is the internal contextual support for an understanding of the passage.
Level 2. Contextual Evidence – this is support for an interpretational option found in the context of the passage. The closer the context, the higher the value (immediate context is stronger than section context, which is stronger than book context, which is stronger than same writer context, etc.)
Level 3. Lexical Evidence – this is support for an interpretational option found in the specific meaning of words used. Since the meaning of a word is determined by the company it keeps, this category actually overlaps with both syntactical and contextual evidence, but a lexical argument lacking in syntactical or contextual support can sit here at level three.
Level 4. Correlational Evidence – this is support for an interpretational option found in more distant biblical support where the same word or concept appears. After all, a different writer may be using the term in a different way. (Remember that a distant passage that directly influences your focus passage, such as an Old Testament section that is quoted, is highly significant and may be considered as a form of contextual or level 2 evidence.)
Level 5. Theological Evidence – this is support for an interpretational option found in theology, rather than elsewhere in the Bible. This is like correlational evidence, but the correlation is with a theological creed or system.
Level 6. Verificational Evidence – this is support for a position found in “experts” (i.e. commentators, authors, sermons, etc.) It is easy to fall into a false reliance on published books. Simply because a published name agrees with a position is of minimal value. It is so much better to integrate their arguments into the five categories above. That way the commentary becomes a conversation partner rather than a shortcut that always determines your understanding. Much better to weigh the evidence and come to an informed conclusion, rather than reading a commentator and come to someone else’s conclusion.
Remember, this is a guideline, but I think it is helpful. It pushes us to look for understanding within the text itself and within the context.
I do see a lot of people who either don’t wrestle with the meaning of the text in any meaningful way or else are too quick to accept the conclusions of others – either their preferred system of theology or their favourite commentator or preacher. Looking up a passage in two or three commentaries does not equate to exegetical effort.
We have to recognize the spiritual gravitas and countless other personal and ministry benefits that only come from diligent exegetical labour.
Biblical Preaching 
I understand that this might fall under one or more of the headings — but Historical Understandings — what have some of the oldest saints and writers, near the first century, understood the passage to teach. At times it is surprising that historical theology is ignored — some “unique” understandings and interpretations of various passages are completely at odds with what the passage was understood to teach by the early church fathers — i.e. “no room at the inn” is now understood as Mary & Joseph stayed in a room in a relative’s house, no longer the stall of a commercial inn. — just saying you might want to read what the understanding was in the early centuries
This is a good point. And it is important to keep perspective with early centuries … I’ve seen people give perspective from the early centuries a special place of honour, as if a comment by a writer from the other end of the Mediterranean is the definitive word on a matter of interpretation, rather than recognizing the potential for significant error in those writers too. We have to evaluate, but we certainly err if we don’t even consult a potentially valuable source of insight.