See, I grew up in a Southern Baptist church, where "the Tribulation, Rapture and other 'plot points'" were sprinkled on our snacks and in our Kool-Aid;
Yeah, but didn't anybody ever actually read the Bible and come back with "Hey, wait a minute, that stuff isn't in here?" (Go to an on-line Bible and try a keyword search on "rapture," I can guarantee you'll come up dry in the text.) I always thought it was a conceited belief of Lutherans that Baptists never actually read Scripture. Truer than I thought?
(That said, my Mom, who is a die-hard Lutheran, is also a huge Left Behind fan. In the interest of family peace, I've never hit her with the "where is this?" question. Feel free to call it cowardice...)
Well, here's the really ironic thing about it: all we ever DID was read the Bible. Here is a quick breakdown of activities in the average Southern Baptist Convention approved Sunday morning Bible study:
1) Use the scripture to reinforce the danger of disobeying God (pick any Old Testament story for this, and you can't go wrong)
2) Use scriptures to assert the direct authority of Jesus over that of any human being (They love their St. Paul; this exercise is partly intended to undercut any kind of priesthood, and partly to assert personal interpretation as superior)
3) Use the scripture to disect every other religion or denomination, and dismiss it as some kind of cult (We had an annual, weeklong seminar devoted to this... a "con", if you will)
4) Use the scripture to single out proscribed behaviors and demonstrate how they incur the wrath of God (tolerating homosexuality = rain of fire from heaven; lying = consumed by worms; etc.)
5) Use the scripture to show how following Jesus leads to a euphoric kind of joy, which those poor sinners are missing out on
Once the idea of authority is established, and all others have been discredited (leaving the preacher as the only remaining voice of reason, of course), then it's easy enough to get away with taking Revelation and playing the "horoscope" game with it; take it verse by verse and say "this could mean that" pointing to scary events that have taken place and showing how they were "predicted". (I could try to dredge up a couple of examples, but I think you get the idea.) The word "tribulation" actually IS in at least one translation, but it doesn't need to be; the Tribulation is a Big Scary Post-Apocalyptic span of events, so they just take the events that are so colorfully described by John, and say "that's the Tribulation". Same basic idea with the Rapture; it's not called that in the Bible, but the concept of the Saved being taken to Heaven is described in detail, and that is what they focus on.
As for the really crazy stuff that people come up with, they mostly come up with that on their own to fill in the gaps in history that the church ignores. Notice that the narrative of the actual Bible only takes us up to about A.D. 63 or so; for the Southern Baptist church, the time between then and ~1860 is a big, grey void in which the Catholics subverted the "real" Christians, who passed the "real" scripture down through their families until arriving in America where they were free to preach the Word again. This is why you won't make any headway with them by asking about actual Biblical history... all of that "history" was written by the Catholics, so it must be suspect, right?