1. Realize we all are sinners:
"For all have sinned, and come short of the glory of God." (Romans 3:23) Yes, you too have fallen short of Heaven because of your sin. Sin is breaking God's law, the Ten Commandments, like lying, stealing, and disobeying your parents. You may be better than many others, but compared to Jesus "there is none that doeth good." (Romans 3:10-12) Your heartfelt response ought to be, "God be merciful to me a sinner." (Luke 18:13) God wants you to be sorry about your sins and tell Him you see now that you are a guilty sinner.
2. Realize there is a punishment for sin:
"For the wages of sin is death..." (Romans 6:23a) There are two kinds of death, physical and spiritual. One we inherited from Adam and the other we earn by our commitment of sin. If we die in this condition without Jesus Christ as our Saviour, we must die a second (spiritual) death, eternally separated from God in hellfire "which is the second death." (Revelation 21:8)
3. Realize that Jesus Christ, God's perfect sacrifice, has already paid for our sin debt in full:
"...Christ died for our sins." (I Corinthians 15:3) When Jesus died on the cross, He paid for all of our sins with His precious blood and bridged the gap that separated us from God. You must realize that Jesus Christ was not a sinner but God in human form and that God took all of our sins and placed them on Jesus at the cross. While Jesus was bearing all our sins in his own body, God punished Him in our place to pay in full the debt that we owe.
4. Realize you must receive Jesus as your Saviour by faith and accept His free gift of eternal life:
"But as many as received him, to them gave he power to become the sons of God..." (John 1:12a) "...but the gift of God is eternal life through Jesus Christ our Lord." (Romans 6:23b) "For whosoever shall call upon the name of the Lord shall be saved." (Romans 10:13) Whosoever means you. If you by faith and in prayer will trust in Jesus Christ and His death, burial, and resurrection for your salvation, and ask Him to forgive you of your sins, you can be 100% sure that you are going to Heaven.