"One of the first and easiest questions to ask is does the group you are looking into simply make the claim of being the one and only Church Jesus established and must be obeyed. You would be surprised how many Protestant denominations wont make such a claim, this isnt even about proving the claim but simply making the claim. But if the group wont make even the claim then I can count them out off the bat."
You're making some dubious assumptions. A person can believe that Jesus established a church that's existed since the time of the apostles without believing that the church in question must always exist in the form of one denomination. If denominations A, B, and C exist in one century, and denominations X, Y, and Z exist in another century, a person can believe that all six denominations qualify as part of the church Jesus founded, even though some or all of those denominations are wrong on some issues. If they're all correct on the issues that are essential, then they don't have to be correct on every other issue in order to qualify as part of the church Jesus established. Or a person could maintain that the church that's always existed consists of regenerate individuals, regardless of their denomination or lack of denomination. Or a person could maintain that the Biblical evidence for a continually existing church is sufficient grounds for believing in such a church, even if he isn't aware of documentation of that church's existence for every part of church history. Etc. It's not as if belief in a church that exists from the time of the apostles onward requires belief in one denomination that's always existed. You're making some dubious assumptions that don't follow from the premises.
And what does "must be obeyed" mean? Some authorities are fallible. One authority can be subordinate to another. Parents and government officials have authority, but it can be acceptable to disobey them at times, when what they command conflicts with what a higher authority commands (a parent commands a child to follow Islam, a government official commands a woman to have an abortion, etc.). A Christian church can have authority without being infallible.
It's not as if the Biblical passages about the nature of the church are the only criteria we have to go by. Scripture also tells us some things about the identity of Jesus, justification, and other issues. Even if Roman Catholicism were the only denomination claiming a continuous existence since the time of the apostles, we would still have other apostolic standards by which to judge Roman Catholicism: what it teaches about the deity of Christ, the resurrection, justification, etc. If Catholicism seems to be wrong about justification, and scripture defines that error on justification as an error of a foundational nature (as in Galatians), why should we follow Catholicism on the basis of its status as the only denomination claiming continuous existence since the time of the apostles? If you're suggesting that the need for a denomination that's continually existed since the time of the apostles should cause us to question our judgment about justification, then why couldn't we reverse the two? Why not take Catholicism's erroneous view of justification as an indication that we must be wrong about the need for a continuously existing denomination?
But the idea that there must be one denomination in continuous existence is dubious. Nothing Jesus and the apostles taught suggests that there must be one denomination that exists throughout church history. Roman Catholicism's claim of continuous existence is dubious, and Catholicism is disqualified on other grounds anyway, namely its false view of justification.
As an illustration of Nick's oversimplified view of the nature of the church, here's something he wrote in response to Steve Hays in the same thread linked above:
"A divine institution does not mean invisible, as the Church in Acts was clearly visible and the only Christian institution there was. Unless there was a 'Christian institution' that has remained orthodox from the start the Church (of Acts) had to have apostatized."
Nobody denies that there were physically visible entities involved in the book of Acts, such as bishops and congregational meetings. Does it therefore follow that the same physical manifestations must exist at all times? No. (And many of the physical manifestations in Acts, such as the apostolic office and miracles, haven't existed at all times in the Roman Catholic denomination.) Does it therefore follow that the church in Acts existed only where such physical manifestations were present? No. Many individuals were added to the church in a sense, by means of faith, before they ever attended any congregational meetings or identified and submitted to any local bishop (Acts 2:41, 4:4, 8:1-7, 19:1-6). In another sense, though, it could be said that they didn't become part of the church until they joined some local congregation.
The term "church" is defined in different ways in different contexts. If Nick wants to argue that some particular definition of the church must be manifested throughout church history, then he needs to demonstrate that that definition of the church must continually exist. It's not enough to cite one Biblical passage about some sort of church, then cite another passage about some sort of church, then combine the two under the assumption that every passage mentioning some sort of church must be addressing the same entity. To go from the visible manifestations of Christianity in the book of Acts to the conclusion that there must be one denomination that exists throughout church history, in a manner like what Roman Catholicism claims for itself, is quite a leap.
Nick also wrote the following in response to Steve:
"But two denominations can never be as good as one another and yet have both be true. Thus if there is one true Gospel then only one denomination can be holding it, and that denomination is the one true Church by definition."
Again, notice how much Nick oversimplifies the issues he's discussing. Two Baptist groups can be classified as two different denominations, because they're governmentally independent of one another, even if they teach the same gospel. The existence of two denominations doesn't require the existence of two gospels. Groups can be governmentally independent of one another because they believe that churches don't need to be governmentally united, even if they agree with each other on essential issues. Baptists and Presbyterians will often meet together and consider each other brothers and sisters in Christ, even though they're governmentally independent of one another and disagree on some issues. What if two denominations were founded by two men who lived hundreds of miles apart from each other and never met? It doesn't follow that one of those two denominations was ever meant to oppose or replace the other. And even if there was some sort of sin involved in the founding of a denomination, people joining that denomination a few generations later aren't necessarily endorsing that sin, nor are they necessarily even aware of it.
If a person is born into a world with thousands of churches and denominations, then the importance and plausibility of sorting through all of the issues involved in the founding of each denomination are diminished. While avoiding unwarranted divisiveness is important, so are other issues in life. If a local Anglican church claims a succession from the apostles, but is unfaithful to much of what the apostles taught, while a local Baptist church is more faithful to apostolic teaching and claims no such succession, why are we supposed to think that the Anglican church would be preferable?
Nick tells us "if there is one true Gospel then only one denomination can be holding it". Does it therefore follow that Eastern Orthodoxy, for example, has a false gospel? What about the church fathers who were out of fellowship with the Roman church of their day? Were they following a church with a false gospel, since their church wasn't governmentally united with the Roman church?