1. A Good Hermeneutic ... since you have to have a framework for intelligible communication.
2. A Good Systematic Theology ... because the Bible only has one system of truth (though it may at times be confusing to our human finitude) and every text has to fit with every other.
3. A Good Understanding of the Text ... because you have to know what God said and what he meant when he said it.
4. A Good Understanding of Your Audience ... because you have to know where they live in order to communicate the meaning of the text in its theological context in a way that they will understand it.
5. The Ability to Communicate ... so that your audience will be able to grasp God's word for their lives and be challenged to live by it.