Spurgeon on preaching the Gospel:

It is ours to give men something worth their hearing; to instruct them.  We do not preach the gospel unless we teach the great truths of revelation.  The gospel is good news…there is information in it, there is instruction in it concerning matters which men need to know and statements in it calculated to bless those who hear it.  It is not a magical incantation, or a charm, whose force consists in a collection of sounds; it is a revelation of facts and truths which require knowledge and belief.  The gospel is a reasonable system, and it appeals to men’s understanding; it is a matter for thought and consideration, and it appeals to the conscience and the reflecting powers. Hence, if we do not teach something, we may should, “Believe! Believe! Believe!” but what are they to believe?  Each exhortation requires a corresponding instruction, or it will mean nothing.  “Escape!” From what?  This requires for its answer the doctrine of punishment for sin. “Fly!” But where?  Then you must preach Christ, and His wounds; and the clear doctrine of atonement by sacrifice. “Repent” Of what?  Here you must answer such questions as, What is sin?  What is the evil of sin?  What are the consequences of sin?  “Be converted!”  But what is it to be converted?  By what power can we be converted?  What from?  What to?  The field of instruction is wide if men are to be made to know the truth which saves, “That the should be without knowledge, it is not good,” and it is ours as the Lord’s instruments to make men so to know the truth that they may believe it, and feel its power.  We are not to try and save men in the dark, but in the power of the Holy Spirit we are to seek to turn them from darkness to light.

And, do not believe, dear friends, that when you go into revival meetings, or special evangelistic services, you are to leave out the doctrines of the Gospel for you ought to proclaim the doctrines of grace, simply, and plainly, and especially those truths which have a present and practical bearing upon man’s condition and God’s grace….

People do not get true healing because they do not know the disease under which they are suffering; they are never truly clothed because nothing is done towards stripping them; He does not quicken them by the Gospel till first they are slain by the law…The preacher’s work is to throw sinners down in utter helplessness, that they may be compelled to look up to Him who alone can help them. 

Source: What is it to Win a Soul in The Soul Winner by Charles Spurgeon