In any text there are at least two necessary roles, but with Scripture and many other documents, there are three—the author, the original audience, and the interpreter. All are important although all have different roles in the communication process. The author holds the meaning and is responsible for conveying that meaning to the audience. The audience is responsible for trying to understand the author’s meaning. And the interpreter has a further responsibility of trying move through some combination of time, geography, language, and culture to understand how an original audience would hear and understand the author’s meaning.
It is important to remember that the author gives the meaning to the text because it is the meaning that purposed the text in the first place. In the case of the Bible, there is a duel divine and human authorship. In this case, there is a possibility that the original audience may have misunderstood the divine author’s intent. There is also a possibility that a later interpreter, thousands of years after the authorship of the text, can miss the human author's meaning, or both. But because it was the author that tried to communicate the meaning, it is not possible that the author miss the meaning of the written work. It is here that one might argue that there is no way Isaiah could have fully understood his written prophecy about Christ, but we must remember that God is divine author of Scripture.
So as one ventures into Scripture, it is important to practice good hermeneutics. Simply remembering the three roles is a very significant first step that will generally help every student of the Bible. I tend to first ask, "What did it mean then?" Only after I've developed an answer to this questions do I ask, "What can I learn from this passage as it was intended and how can I apply what I've learned to my own life?"
Grudem, Wayne A. Systematic Theology: An Introduction to Biblical Doctrine. Leicester, England: Inter-Varsity Press, 1994.