A person must believe that they have sinned
"For all have sinned, and come short of the glory of God" (Romans 3:23)
A person cannot work their way to Heaven
"Not by works of righteousness which we have done, but according to His mercy He saved us..." (Titus 3:5)
"For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast" (Ephesians 2: 8-9)
A person needs to know that there is a price for sin
"For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord" (Romans 6:23)
A person needs to know that Christ paid the price for their sin
"...Christ died for our sins according to the scriptures..." (I Corinthians 15:3)
"For he [God] made him [Christ] to be sin for us...that we might be made the righteousness of God in him [Christ]" (II Corintians 5:21)
A person must ask Christ to be their Savior
"For whosoever shall call upon the name of the Lord shall be saved" (Romans 10:13)
A person might pray something like the following:
Dear Lord,
I know that I am a sinner, and I need to be saved. I believe that Jesus Christ died for my sins and was buried and rose again the third day. Forgive me of my sins, come into my heart.
In Jesus' name,
Amen