Revelation 12:11 "And they overcame him by the blood of the Lamb, and by the word of their testimony"
Some times when you can't think of what to say, just tell them your story of how you came to the LORD JESUS.If maybe this will help, just tell them your testimony and in some way if you can work in the Ten Commandments, maybe like when you are telling them why you knew you needed a Savior, because you got to thinking about what Commandments you knew you had broke and then just tell them your story of how you knew you needed to Repent and put your Faith not just some but all 100% Trust and Faith in JESUS and HIM alone to Save you from sin and hell.
Just remember your testimony is a strong witness to people, and one thing most important is it's your testimony and no matter what they say or think it's your testimony and they can't argue with you about your testimony.
So if you have a loved one or friend you need to talk to just Pray for the LORD JESUS to help you then just give them your testimony.
Just remember also JESUS will be there with you and when you are weak, HE will be your strength if you just pray for HIS help. ( that's when HE gives you strength when you know you are weak and need HIS help, so just get to your knees to pray, then HE will lift you up and give you the words to say!)
May the LORD bless you in reaching the lost souls out there!!