we need to look at the big picture - the themes that are consistent throughout scripture - not the fine detail, for our understanding about authentic Christian lifestyles.
I should first make a confession: I’m a Quereinsteiger into theology, so my knowledge is limited to what I’ve read, which is for now mainly Childs and Barth. From what they say, a focus on the “big picture” would seem to be the best way to preach. Your average congregation member is going to be looking for ways to live their life in the fullness of what Christ has done, as well as to understand this fullness. Given that this reality is not available in any one text, it is the totality of Scripture that provides the most adequate context for accessing and proclaiming this truth. As Barth says, a theology which is orientated to him who is its starting point and goal must thus become “a knowledge that articulates the unity of the manifold.” Whatever text constitutes the reading for the day, in the act of preaching the logic of the Gospel requires that it be taken up into the whole and be seen in relation to this whole. A syn-opsis, a seeing-together, needs to take place.
I should add that this happens anyway. No one reads a text in isolation from the multitude of intertexts that are already present in his or her head. As such, a preacher should not only be theologically trained in learning how to relate the parts to the whole (Childs’ canonical approach?), he should be a faithful disciple, steeped in his tradition, so that, whether consciously or not, he becomes an adequate “intertextual hub,” presenting the Gospel as fully as possible.