How can I know for sure that I will go to Heaven when I die?"
Do you know for certain that you have eternal life and that you will go to Heaven when you die? God wants you to be sure! The Bible says: “I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life” (1 John 5:13). Suppose you were standing before God right now and He asked you, “Why should I let you into Heaven?” What would you say? You may not know what to reply. What you need to know is that God loves us and has provided a way that we can know for sure where we will spend eternity. The Bible states it this way: “For God so loved the world that He gave His only Son, that whoever believes in Him shall not perish but have eternal life” (John 3:16).
We have to first understand the problem that is keeping us from Heaven. The problem is this - our sinful nature keeps us from having a relationship with God. We are sinners by nature and by choice. “For all have sinned and fall short of the glory of God” (Romans 3:23). We cannot save ourselves. “For by grace are you saved, through faith, and this not of yourselves – it is the gift of God. Not by works, so that no one can boast” (Ephesians 2:8-9). We deserve death and hell. “For the wages of sin is death” (Romans 6:23).
Read more: http://www.gotquestions.org/know-sure-Heaven.html