The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach. -Romans 10:8
Chances are someone else has already planted the seed of truth within your heart and, as you're reading this, I am watering it; or maybe you are hearing the gospel for the first time. Either way, you and I just fulfilled this verse of Scripture--I am "preaching" the Word of God, and you now have everything you need to believe it.
The choice to believe is yours. However, you can't say that you don't have what you need to believe, because I have just given it to you. The Bible says, "The word is nigh thee," meaning everything you need in order to believe is there; just believe.
So will you make the decision to believe God today? (Notice I didn't say believe in God. Even Satan believes in God. I just said believe God--believe that what He said in His Word is true.) All you have to do is to turn completely from your sins and trust in the Savior to save you. You don't even have to start living "right" first--your trusting in Jesus will cause you to want to live for Him, but you could never live for Him without first trusting Him.