From time to time I have tried to give preaching advice. It usually comes out muddled. The great Pr. Esget has some great advice on preaching. He boils it down to this:
- Preach the Sunday.
- Don’t impose Law and Gospel as a structure on each pericope. Most of them don’t work that way, and you’ll corrupt and distort the message of that text.
- Preach expository sermons at least some of the time
- Don’t preach the cross without the resurrection.
- Ignore most commentaries. They’re useless. Do your own exegesis, and then read the fathers. Luther if you have time.
To which I can only add : Amen and Amen!
Musings of a Circuit Riding Parson 
While I agree a Law then Gospel outline is not appropriate for some texts, one caution is necessary here. Neither Law nor Gospel can be absent from any sermon – ever.
If a pastor every preaches a sermon in which there is no Law or Gospel because he could not find it in the assigned text then, frankly, he better damn well resign from the ministry. If you can’t find Gospel in the pericope you have chosen (and I have yet to find a single Sunday in which the Gospel was not clear in at least one of the readings) then expand the pericope. The Word is inspired – which readings are selected for a Sunday and where they begin and stop is not. If you have to go a few verses earlier or a few verses later to find Gospel then do it. For if you don’t preach Gospel then you have not preached Christ.
I have heard and read way too many crappy sermons lately in which the Gospel was so feeble as to be non-existent. I have heard others in which the Gospel was proclaimed but, because there was no Law, the Gospel was merely a message of God’s abundant fondness for mankind rather than real forgiveness. Such sermons may be educational but they are not proclamation. just as you should never preach the cross without the resurrection neither can you ever preach the Law without the cross.
The Law and Gospel must be clear and present in every sermon regardless of the outline used the Gospel must predominate in every time. Period.
So just because a pastor may not use a Law/Gospel outline doesn’t mean he can drop either one.
Agreed. I think the point is not to try and impose a structure on the reading that is not there. But you are correct. Law and Gospel must be present. It is easy to fall of the horse the other direction.