1 John 5:6 "...And it is the Spirit that beareth witness, the Spirit is truth." When I think I may have an opportunity to witness I say a silent prayer asking God to use me to convey what He wants the other person to hear. At that point I can relax and then I'm amazed at how I bring up God in the converstion. I can't remember the scriptural reference, but the Apostle Paul wrote that he planted, Apollos watered, but God kept making it grow. With these simple concepts in mind, I usually relate my personal experience and then I encourage personal prayer. I teach people to pray in the name of Jesus Christ because he died for our sins and was ressurected. In this way I convey that a personal relationship with God is real and that Jesus died for our sins. I figure that's enough for people to start with. I don't give people an overload of information because I want them to remember what I said. God will bring back to their minds these simple points which allows them to ponder the matter and perhaps reach out to God.