This friend happens to be a non-believer who would like to pray for another friend (a believer) who is going through some difficult times.
If your friend is a nonbeliever, the first prayer I would suggest for him or her to pray is “God if you are real, then reveal yourself to me. I don’t know if you’re real. I don’t understand everything. But I’m open to believing.”
If your friend comes with a humble attitude rather than a mocking one, I believe God will arrange the circumstances in his life so that she will get to know God. This is where God will use people like yourself to tell your friend about your own relationship with God and how to get to know Him for herself. At some point you’ll want to explain to her about turning away from our sins and trusting in God for our salvation. You’ll want to show care to your friend and the person she is praying for, yet at the same time not give the impression that God is some magic genie who will answer all our prayers. What I suggest you do is to pray with your friend and model prayer for her. Most people learn how to pray by hearing someone else pray not reading some book.
[Answered by Pastor Quang]