Congrats, that is a great feeling and one of the more valuable ratings you will hold.
You can't force the flying bug into anyone, just be friendly, let them ask questions, and make the flight as all around as enjoyable as you can. Explain things to them, try to remember what it was like when you first flew a small aircraft and use that to relate. I've found if you can get them to laugh and smile, things tend to go much better. They will already be nervous enough.