The Bible must be interpreted as part of a whole. To be more precise, each passage of scripture has 1. This is a rule of intepretation that is quite often broken it seems. New intepretations of familiar passages of scripture often make a mistake of context. Spiritualizing scripture in places that don't warrant this kind of intepretation often breaks this rule of context.
Words mean things only within their context.
Compare scripture with scripture This may seem like common sense but historically it wasn't always practiced. All truth in the Bible should be compared against the Bible since God doesn't contridict Himself. This of course assumes a belief in the verbal inspiration of scripture. Actually, it's the first and most important truth that has led us to our method of Bible interpretation. Even more important, how can we go to the Bible for spiritual truth if there are errors in the Bible.