There is only one way to make certain that Heaven is our destination when we die. We have to become a genuine born-again Christian, just like Jesus said in John 3:3 and John 3:7, and follow the ways and teachings of Jesus Christ.
Jesus said we must be "born again" before we can see the kingdom of God. Nicodemus was a Jewish priest who went to see Jesus at night. This is described in the Gospel of John.
"Now there was a man of the Pharisees named Nicodemus, a member of the Jewish ruling council. He came to Jesus at night and said, "Rabbi, we know you are a teacher who has come from God. For no-one could perform the miraculous signs you are doing if God were not with him." In reply Jesus declared, "I tell you the truth, no-one can see the kingdom of God unless he is born again." "How can a man be born when he is old?" Nicodemus asked. "Surely he cannot enter a second time into his mother's womb to be born!" Jesus answered, "I tell you the truth, no-one can enter the kingdom of God unless he is born of water and the Spirit. Flesh gives birth to flesh, but the Spirit gives birth to spirit. You should not be surprised at my saying, 'You must be born again,'" John 3:1-7.
Jesus said that none of us would see the Kingdom of God unless we are "born again" by the Holy Spirit. This is a spiritual birth, when the Holy Spirit comes to live in us after we have received Jesus Christ as our personal Saviour. When we do this God adopts us into His family.
If we reject God's plan of Salvation we will not end up in Heaven
If we reject the forgiveness that God offers us then we are turning away from Him, and we remain 'sinners'. The Bible tells us very clearly in John 3:36 that eternal separation from God will be the result of this action: "He who believes in the Son has everlasting life; and he who does not believe the Son shall not see life, but the wrath of God abides on him", John 3:36.
Romans 3:23 says that we are all sinners in God's sight because we have broken His commandments. God is holy and pure and sin cannot exist in His presence. The only way to God is to say we are sorry for the wrong things in our life and accept the forgiveness offered to us, through the Blood of Jesus Christ. This is explained in the next chapters.
Many people in this book have met an angel in Heaven. According to Psalm 91, we all have a personal angel, if we are "born again" into God's Kingdom.