How do you get Salvation?

Salvation
When I restated the question from the Da Vinci Code “What if Jesus was just a great man, what would that do to your faith?” I was asked “What about Jesus dieing for our sins” that bring up a 2000 year old debate do you get salvation from living by the word of Jesus to help your fellow man and forgiving others their sins or by believing that Jesus the son of God died for your sins on the cross. Actually it might be a two question test and you have to do both, but if only one gets you Salvation which is it? Now most churches will say you have to believe that Jesus died for our sins on the cross because then you have to come to them for salvation, but if doing good works and forgiving others get you salvation you don’t even have to be Christian. Which is right? Hey! I am just a common old working man how do I know?