There are three things that Jesus taught during His ministry, to call people to Himself. Firstly, He taught people to repent from sin (Luke 13:3, Mark 1:15). Secondly, He taught people to believe in Him (John 3:16-18, John 11:25, John 14:1). And thirdly, He taught people to follow Him—to be His disciples (Matthew 10:38, Matthew 16:24, Luke 9:23, Mark 10:21).
He promised eternal life to those who did these things. We are preaching correctly if we preach these three things also.
Step 1: Repentance
To repent means to change one's mind. Since we're specifically to repent from sin (Hebrews 6:1-2), this means that we're to turn away from any thoughts, words, and actions that are sinful. Jesus repeatedly said it this way: “Go and sin no more” (See John 5:14, John 8:11). The call to repentance is the first step in the call of the gospel (Luke 24:46-47).
Keep in mind that this doesn't mean a person must have perfect repentance before they can follow Jesus. It simply means that when one comes to Christ, they must make a decision to turn away from any sin that they're convicted of or that they discover in their life. Repentance will be progressive. A person will repent of more as they learn more about what sin is and what sin they have in their life. The initial repentance that saves is simply the heart-change that produces the decision to start repenting of sin.
Step 2: Belief
Upon the decision to repent, we must know what we are turning to. We are turning to God and to His Son, Jesus Christ. We are called to turn to Jesus, first, by trusting in His death to take away our sins and by believing all of His words. This means, practically, that we must preach that people must believe with all their heart that Jesus Christ is Lord, that He died and rose again, and that the Bible is truth to be obeyed (Romans 10:9-10, Matthew 7:21-27).
Step 3: Following/Obedience
Upon genuine repentance and faith, one will choose to become a student of Jesus Christ, endeavoring to learn His word—His teachings—and put them into practice in their daily lives. Believers will make mistakes along the way, but the pursuit of a truly repentant and believing heart is progressive obedience. Discipleship is about growing in knowledge and obedience to the teachings of the Bible.
As it's accurately written in the KJV, “He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him” (John 3:36).