The Bible is its own commentary. This means, we ask was that said before? and if so, where and what was the context? We are to interpret the words literally and in their historical sense, unless the “context” or “manner” in which they are used seems to be out of context or a contradiction or dissimilar. An example would be the OT Prophets or Apocryphal language that would indicate symbolic meanings. This does not diminish the meaning; it actually extenuates it when we have the key to the metaphor, and Scripture is always the key to Scripture.
Did you know that a lot of the Book of Revelation is found in Ezekiel, Jeremiah, and Isaiah, and not so much in Daniel? Thus, before we come to any eschatological conclusions, we are to make sure the passage about which we are reading or writing is clear and is backed up by other passages of Scripture and that we use these other passages to help us make sense of the meaning. For example: there is a lot of confusion over the mark and 666. Many people see them as the mark of the antichrist tricking people into worshipping the beast or himself. Or, a counterfeit Jewish messiah or a slick false preacher is the “false prophet” mentioned in Rev. 16:13. These images bring all kinds of speculations—from an idol coming to life to a robot, a computer chip implanted in people, or some other technology that God can’t do anything about, while others see this as the rebuilt Temple captivating people. The mark and buying and selling are also seen as the world changing to a cashless society, ripe for corruption and control by the antichrist. One crazy theory after the other appears while no one seems to bother to take a look into the Old Testament such as Ezekiel 9:4-6 that John was quoting and see what these images meant, or look at Deuteronomy 13:1-11; or John Himself telling us what the antichrist is all about in 1 John 2:18, 22; 4:3; or 2 John 1:7. Not sure? See for yourself on the Bible study in Revelation 13:11-18, http://70030.netministry.com/articles_view.asp?articleid=33585&columnid=3803&contentonly=true
This rule is simple: we use the Bible to see what other parts of the Bible say and this clears it up. What we do not do is come up with a theology by ignoring contexts, word meanings, and other passages. The Bible does not contradict itself; it does bring more light and insight, so use it.