The next time you have the opportunity ask a Christian friend to explain the gospel. Also be sure to add that you want it supported with Scripture. Even though they may have heard it for years, if they aren't able to verbalize clearly, then they really don't understand it. So with that in mind listen to Kirk Cameron ask Dr. John MacArthur about the gospel. For those who God places in your circle of influence, it may be a matter of life or death.