What do you tell a person that is not a Christian?  What if a person does not know whether he is born again.   What do you do?  Your friend thinks he is a Christian, but you know better.  What do you tell them?
     There are some "life and death" statements in the Bible that should get your attention.  "Unless you believe that I am He, you shall die in your sins"  (John 8:24).  Another is "...Jesus shall be revealed from heaven with His mighty angels in flaming fire, dealing out retribution to those who do not know God and to those who do not obey the gospel of our Lord Jesus.  And these will pay the penalty of eternal destruction, away from the presence of the Lord and from the glory of His power."  (2 Thessalonians 1:7b-9). 
     It is imperative to believe that Jesus is who he said he was, to know God and to obey the Gospel.  However, there seems to be a recurring problem in telling the Gospel.  The message of the Gospel is either incomplete or non-existent.
     What is the Gospel?  The word literally means "Good News".  What is the Good News?  Paul tells what the essence of the Gospel is:  "Now I make known to you brethren, the gospel which I preached to you, which also you received, in which also you stand, by which also you are saved, if you hold fast the word which I preached to you, unless you believed in vain.  For I delivered to you as of first importance what I also received, that Christ died for our sins according to the Scriptures, and that He was buried, and that He was raised on the third day according to the Scriptures.  (I Corinthians 15:1-4)
     Notice that the Gospel is what saves.  Notice also what the Gospel (the "Good News") consists of:  Jesus died for our sins, was buried, and was raised on the third day.  That is the heart of the Gospel message.  Paul even stated that he delivered "as of first importance" these facts.  Bottom line:  The Gospel is that Jesus died for our sins, was buried and raised.
     The Gospel is not the "one true church", it is not "instrumental music", it is not even "baptism".  To often we have a tendency to jump into those discussions.  Even more, we are led by others into talking about all of these side issues without ever getting to the point.
     What is the point?  The destiny of their souls!!!  Only the Gospel has the answer to that.  Jumping into Baptism without sharing the Gospel is getting the cart in front of the horse.  Those are not the things the Paul said were "as of first importance". 
     Don't misunderstand,  the Bible is clear about the necessity of baptism. However, the object of our faith is not in baptism, but in the resurrected Lord Jesus.  When Peter preached the first Gospel sermon in Acts 2, he preached Jesus as the promised Messiah.  It wasn't until the people were "pierced to the heart", and were ready to do something about it that Peter preached Baptism.
     To preach Baptism to wash away your sins without first preaching the blood of Jesus which washes away your sins is to reduce the Gospel to a system of works where you merit your own salvation, which is useless.  The power is not in the water, but in the blood. (I Peter 1:18-19)
     So don't get the cart before the horse.  Stick to the Point:  The Gospel.  When speaking to someone that is not yet a born-again Christian, determine to know nothing except "Jesus Christ, and Him crucified" (I Corinthians 2:2).  Decide to open your mouth and preach "Jesus to him" (Acts 8:35).  Pull them, lead them to Christ, don't push them.
     Those that do not obey the Gospel will be damned to Hell, according to the above passage.  So there is an urgency to show the way to be saved, which is Jesus himself (John 14:6).  So the Gospel isn't just news to be heard, but also a call to be "obeyed" - for life.  This obedience involves repentance which initially leads to Baptism & Forgiveness.  This is the beginning of a new life (Colossians 2:12; 3:1).   Just the beginning.  Christians must be "faithful until death" (Revelation 2:10).
     So, remember to stress these concepts FROM READING THE OPEN BIBLE when preaching the Gospel.
          1.  Sin Problem
          2.  God's Solution - Jesus
          3.  Your part
     If being reminded about what the Gospel is gives you a better handle on it then it's time to "Go into all the world and preach the gospel to all creation" (Mark 16:15).