Appeal to inspiration by the Holy Spirit, of course, does raise the uncomfortable question of who validates that inspiration – no problem among a group who believe alike, but the Holy Spirit has been loath to convince Diogenes or Gaudere of the accuracy of my beliefs, up to this point in time at least. 
However, Izzy, perhaps an appeal to our legal system will clarify how I see things. Administrative regulations must conform to the language of the statute authorizing them; no bureaucrat can decide that, e.g., the sale of tetraethyllead-containing gasoline is a bad thing environmentally and prohibit it by promulgating a regulation; he must first convince Congress or a state legislature that it has strong negative environmental impacts and get them to pass a statute prohibiting sale of such gasoline – then he can write his regulation. And Congress and the legislatures are bound by the terms of the Constitution, and cannot pass laws that contravene what it says. Nor can a court enforce a validly-passed statute in a way that violates the constitution – e.g., if it’s illegal to go over 45 MPH on this stretch of highway and people of all kinds regularly exceed that limit, but only black men are stopped and given tickets, then while the speed limit is perfectly legal, its enforcement is violating the Equal Protection clause – the police must either enforce it equally against motorists of all races and both sexes, or cease to enforce it at all.
Likewise, and taking the Christian Bible rather than the Tanakh as my basis, I’m given a list of 631 commandments in the Torah and numerous exhortations amounting to commandments in the Prophets. Paul’s letters are full of instructions so phrased as to amount to commandments. And there may very well arise a situation in which two or more of these commandments contradict each other. How, then, will I comply with the law? I have a few guidelines – Paul also says that we are free of the Law, saved by grace to live lives pleasing to God as guided by the Holy Spirit. But most emphatically, Jesus gave a specific on what behavior God expects in identifying two of those 631 commandments and setting them above the others, and in His parables giving examples of how one carries out the will of God in holding those two as “God’s constitutional standards,” so to speak. This is without going outside the bounds of the Bible itself – the intrinsic standard, as it were.
When I do go outside the bounds of the Bible, I find that the book itself can be critiqued by the standards of textual criticism applied to every sort of ancient manuscript. While some such critics may bring unpalatable assumptions to the table (e.g., the idea that predictive prophecy is not possible, so alleged predictions of future events must have been back-written), I may still use the paleographical, linguistic, and cultural-anthropology information I can accrue in an effort to understand better what the Bible says. The bit about Sarah being Abraham’s sister, for example, is explained by a custom recorded in the laws of, IIRC, Ebla, where the bride of the heir is formally adopted into the family of the heir, meaning that her birth family is not entitled to a claim to the family possessions because she is now a part of the new family – but also meaning that she marries the man who has just become her adoptive brother. This may or may not have anything to do with the business about Terah being Sarai’s father or with the two stories where Abraham passes her off as his sister to two kings in whose territory he is traveling, but it may very well be an illumination of that story that clarifies what’s happening in them – Abraham is not lying per se but taking refuge in a legal technicality, so to speak.
In addition, I have the appeal to tradition – what have the vast majority of orthodox Christians over twenty centuries understood to be the truth? – the appeal to reason – how does this Biblical statement accord to the truth about the world available from empirical investigation? – and the appeal to authority – what do(es) the person(s) whom I and my co-religionists have selected to be our leader(s) and teacher(s) have to say about this Biblical statement?
I am also guided by my ability to recognize literary genre. Jonah, Job, and Esther, for example, bear every evidence of being literary works – stories told to convey a particular ethical or metaphysical point or points, and in the last case to provide a background for the celebration of Purim. The third chapter of Habakkuk speaks to anyone with an ounce of emotional resonance in them of a man who, beset by personal disaster and desperation, takes refuge in the might of the Lord. Psalm 130 speaks to anyone who has ever felt despair. I need not accept at face value the imagery of the avenging warrior in Habakkuk or obtain a precise scientific measure of how much the watchman relies on the coming of the dawn in the psalm in order to find truth in the words of those two passages.
