To be an effective witness we must get the word of God inside of us. One way to have the word in you is by memorizing key Scriptures of the Gospel. Here are some of my favorite:

Ephesians 2:8-9 “For we are saved by grace through faith, not by our own works so that no one may boast.”
John 17:3 “Now this is eternal life that they may know You, the one and only true God and Jesus Christ, whom You have sent.”
Romans 6:23 “For the wages of sin is death, but the free gift of God is eternal life through Jesus Christ.”
II Cor 5:17 “If anyone is in Christ he is a new creation.”
John 3:16 “For God so loved the world that he sent his one and only Son that whoever believes in him shall not perish but have eternal life.”