Most people understand that doing evil can keep us out of heaven. But few realize the Bible also teaches that doing good cannot get us in. None of us could ever gain enough merit to deserve heaven. We are sinful, and God's standard is utter perfection. Jesus said, "Unless your righteousness exceeds the righteousness of the scribes and Pharisees, you will by no means enter the kingdom of heaven" (Matthew 5:20). He added, "you are to be perfect, as your heavenly Father is perfect."
Then who can be saved?
The disciples asked Jesus this same question (Matthew 19:25). His answer? "With men this is impossible, but with God all things are possible" (v. 26). In other words, our salvation is not something we can accomplish. It is something God must do for us.
READ MORE: http://www.gty.org/resources/questions/QA102/how-good-do-i-have-to-be-to-go-to-heaven