I've been thinking a fair bit recently about how I see what preaching is and how I go about it. This is very much a first attempt to write something down about it.
Preaching as Proclamation
I guess the classic model of preaching is that it's about bringing God's word to the people – basically telling them what God says to them, specifically through the Bible. I think that's an important position to start from, and I think it is absolutely critical to remember that we can only tell authoritatively that God is saying something if it's in the Bible, so therefore in as much as preaching is meant to be speaking from God, it should also be speaking from the Bible.
I think that where this model breaks down is that it fundamentally assumes an ontological distinction between the preacher (who is seen as being able to interpret the Bible almost authoritatively) and the congregation. So it works fine as a model if you've got an Old Testament prophet (well, a true prophet, not a false one), with God speaking to them directly and authoritatively, and to an extent in evangelism where the preacher can be assumed to have a better access to God's truth than the hearers he's aiming at (though he shouldn't take it for granted that they will necessarily agree that he has. If they don't, this model probably breaks down there too).
Bible Reading as Encounter
I guess where I'm coming from in my understanding of preaching is my understanding of what personal reading of the Bible should be about. The Bible is all about Jesus, and it points to Jesus. That's what it's for (e.g. Luke 24:27). So the point of reading the Bible is to meet Jesus in the Bible. When we read the Bible for ourselves, we should be encountering Jesus in it, and that encounter should change us, because the Christian life is about being continually transformed by the renewing of our minds.
If the Jesus I meet fits in perfectly with what I already thought about him and with how I already lived, then I am unlikely to change because there is no need to change. If I am going to change, I need to see how the Jesus I meet in the Bible does not fit with my conception of him, or does not fit with the way I live my life. Bible study then should be profoundly transformative, as we find that Jesus does not fit into the box we have made for him in our lives. And transformation is often uncomfortable.
Preaching as Encounter
What I think the point of preaching is then is to lead people into the Scriptures, where they encounter Jesus. It isn't to explain the passage – it's to help them to meet Jesus in the passage. That might well include explaining the passage, and usually should, but explaining the passage isn't the main point of what we're doing when we preach, and neither is giving people tips on 7 ways to improve your prayer life, though there might well be a place for that as a consequence of meeting Jesus, especially if we meet Jesus as he is teaching us about prayer, for example.
When we lead people to encounter Jesus in the Scriptures, we need to know the way, which I think is the main point of studying the passage in detail beforehand. If we know where Jesus is in the passage and how he changed us as a result of our encounter with him in the passage, we can avoid the dead ends and lead people along the route we have already travelled to Jesus, and show them how our encounter with him has changed us. Preaching then may well involve revisiting Jesus in places where we ourselves have recently experienced discomfort and pain through the encounter.
It may be that the main way in which an encounter with Jesus in Jeremiah 13 (for example) changes me is different from the way that encounter should change many of my listeners. In that case, we need to identify as much as possible with our listeners in our own minds before meeting Jesus in Jeremiah 13, so that we can model the change that Jesus brings about.
My thoughts may change as I hear more good sermons and as I get more experience at preaching. But that's where I'm at at the moment.