This is a multi post that will detail some of the things I learned doing my latest paper in my doctoral program.
As man has sought to learn more about God he has developed numerous methodologies. Regardless of the methodology, the Scriptures must be the beginning and end of the research. Yet this does not preclude the use of other genres of literature in the overall process of research. The first focus has been to look at the current state of the Scriptures and then develop doctrines based on the Scriptures. This practice is systematic theology. The second focus is to research the development of the Scriptures over time, which is biblical theology.
Grant R. Osborne differentiates thusly: “Biblical theology studies the themes behind the individual books and traditions within the Bible, seeking covering laws that integrate them into a holistic pattern.” In light of Osborne’s definition of biblical theology, proper research into the underlying meaning behind the various books of the Scriptures brings together historical, sociological, linguistic, archeological, hermeneutical, and exegetical methodologies.
The goal must be not only to understand the meaning behind the books of Scriptures, but also to seek to develop and justify the unity between the Old Testament and the New Testament. Some scholars believe any connection between the two testaments is arbitrary; this point will be examined throughout this paper. The passages selected for review, analysis, and understanding using biblical theology methodologies are Isaiah chapters forty through sixty-six. The first step is examination of the historical traditions and difficulties behind these passages.
 Grant R. Osborne, The Hermeneutical Spiral: A Comprehensive Introduction to Biblical Interpretation, rev. and exp., 2nd ed. (Downers Grove, IL: InterVarsity Press, 2006), pp. 353–354.