Spurgeon lists characteristics of sermons that are likely to be associated with salvation:
sermons which are distinctly aimed at the conversion of the hearers.
sermons that interest the hearers
"The people will not be converted while they are asleep; and if they go to sleep, they had better have been at home in bed, where they would sleep much more comfortably."
sermons that are instructive.
sermons that cause an impression
"Preach, for instance, as you would plead if you were standing before a judge, and begging for the life of a friend, or as if you were appealing to the Queen herself on behalf of someone very dear to you. Use such a tone in pleading with sinners as you would use if a gibbet were erected in this room, and you were to be hanged on it unless you could persuade the person in authority to release you....for they see that then you communicate to them not only the gospel, but yourself also. The kind of sermon which is likely to break the hearer's heart is that which has first broken the preacher's heart, and the sermon which is likely to reach the heart of the hearer is the one which has come straight from the heart of the preacher"
sermons with nothing in them that is likely to divert the hearer's mind from the object we have in view.
sermons which are full of Christ
"Let your sermons be full of Christ, from beginning to end crammed full of the gospel. As for myself, brethren, I cannot preach anything else but Christ and His cross, for I know nothing else, and long ago, like the apostle Paul, I determined not to know anything else save Jesus Christ and Him crucified. People have often asked me, "What is the secret of your success?" I always answer that I have no other secret but this, that I have preached the gospel,�not about the gospel, but the gospel,�the full, free, glorious gospel of the living Christ who is the incarnation of the good news. Preach Jesus Christ, brethren, always and everywhere; and every time you preach be sure to have much of Jesus Christ in the sermon. You remember the story of the old minister who heard a sermon by a young man, and when he was asked by the preacher what he thought of it he was rather slow to answer, but at last he said, "If I must tell you, I did not like it at all; there was no Christ in your sermon." "No," answered the young man, "because I did not see that Christ was in the text." "Oh!" said the old minister, "but do you not know that from every little town and village and tiny hamlet in England there is a road leading to London? Whenever I get hold of a text, I say to myself, 'There is a road from here to Jesus Christ, and I mean to keep on His track till I get to Him.'" "Well," said the young man, "but suppose you are preaching from a text that says nothing about Christ?" "Then I will go over hedge and ditch but what I will get at Him." So must we do, brethren; we must have Christ in all our discourses, whatever else is in or not in them. There ought to be enough of the gospel in every sermon to save a soul. "
Sermons which appeal to people's hearts rather than just their heads
sermons which have been prayed over
"I mean those discourses that have had much real prayer offered over them, both in the preparation and the delivery, for there is much so-called prayer that is only playing at praying.... the way to make sermons is to work vital electricity into them, putting your own life and the very life of God into them by earnest prayer......You must anoint your sermons, brethren, and you cannot do it except by much private communion with God. May the Holy Spirit anoint every one of you, and richly bless you in winning souls, for our Lord Jesus Christ's sake! Amen."