If preaching has no indicatives, it has no gospel: the gospel is, after all, about what God has done for us in Christ, not what we need to do in response. Equally, if preaching has no imperatives, it lacks specificity. We are to respond to the gospel in many and various ways.
Contemporary Evangelical preaching is often moralistic - telling you all the things you need to do to be an effective Christian. I arrive knowing five ways in which I have failed as a Christian and leaving knowing ten ways. A friend of mine calls these "Another brick in the backpack sermons. Lutheran preaching, on the other hand, is allergic to application, leaving application entirely up to the Holy Spirit, not the preacher. Both of these influences can sometimes be seen in Reformed pulpits.
At its best, Reformed preaching balances indicative and imperative, and gets them in their proper order. I approach it as a fourfold process in my own thinking:
1) what is the law of the passage? What duty does it tell me to do, or doctrine does it tell me to believe? This will be relevant even where there are no direct imperatives, for example narratives, where there are examples to imitate or avoid. The focus here is the law's role in exposing our sin and driving us to Christ, showing us afresh our need of the gospel.
2) How is the gospel specifically good news for a sinner like me whose sin has been exposed in part 1? How has Christ perfectly fulfilled the "law" of this passage? The focus here is on the gospel as the remedy for sin (not moral reformation).
3) How would my life be different if I really believed this passage? What would I do, say, think, believe differently tomorrow morning (the third use of the law)? After all, we believe that the Holy Spirit can convict and instruct his people through means, especially through preaching, not just immediately.
4) How is the gospel still good news for me, as someone who will continue to fail in this specific area, and in many others? If you have weekly communion, this is a natural transition to the Lord's Table.
I find this structure helps me to do justice to both emphases, in a way that sends people out with their eyes on Christ, not their own works (good or bad).