It really hurts me to see my non Christian friends. I know where they are headed for. Not all non Christians get drunk, party, or smoke. There are some that lead a moral life, but they still don't know Jesus. They are headed to the same place as the partiers and drunks.
Some people are followers.
So live as a Christian rolemodel. Who knows one day they may show up in church all because of you. Before you go out and witness, ask God for strength to get his message out in a way your friend will understand. Start with a common subject. Then tell how God has helped you in that area of your life.