2 Gospels?
Many pre-tribulational rapture teachers teach that the "gospel of the kingdom" is actually a different one than the "gospel of grace," which is also term not found in scripture. This is one one many examples of human creativity being employed to concoct scriptural support of a doctrine that is not clearly and openly taught anywhere in the Bible. This "two gospel" theory epitomizes the vain efforts of teachers to justify a doctrine that is not scriptural. Once you have two gospels, you can pick and choose which scriptures to apply to which gospel. From there, all kinds of endless eschatological schemes can be imaginatively seen in the scriptures. Any scripture that contradicts the end times teaching is automatically handed over to be applicable to the other gospel. In this way, the teaching can never been wrong.
Rightly Dividing the Word of Truth
Another thing commonly taught is that the Jews have certain portions of the New Testament written to them and not to the church or Gentile followers of the Messiah. This, again, is an effort to slice up the scriptures so that anything that is not in agreement with the pre-tribulational rapture is conveniently re-appplied to a group of people in the future which the church will be raptured away from experiencing. Not only does this make God a respecter of persons, as the Bible repeatedly says He is not, but it slices the Bible up even further than the two gsopel theory.
So, to properly interpret the Bible, one must learn how to "rightly divide the word of truth." This is taken to mean to literally divide the Bible up into two, over and over again. If you read any old Clarence Larkin material, you can see numerous, classic examples of this technique being used to chop the scriptures into sets of two. I have seen numerous teachers take certain verses and slice the sentences into two parts so that they can justify their pre-trib views. "Rightly divide" is better translated as "properly handle" or "skillfully handle." It has absolutely nothing to do with dividing anything at all. But, in spite of this easily discovered fact, teacher after teacher will slice up the scriptures and justify it all with the excuse that they are "rightly dividing the word of truth."
In these ways, interpreting the scriptures becomes comparable to acrobatics.