Let them know that it is appropriate to talk with their professors and teachers. Introduce them to Christian friends. Invite them on family outings, including a tour of the local library. If they have access to a computer, show them how to use the internet. Help parents meet the needs of their children, including appropriate dress for school, getting involved in their children's schooling, controlling children's television viewing.
Students sense when they are merely a target for evangelism.
Your first priority should be reaching out to the student's needs and from there developing a basis to talk about spiritual matters. Avoid arguments or heated discussions. Recognize that many students don't understand that all Americans are not Christians. When it seems relevant, explain that our culture is distinct from our faith. Explain the difference between America's cultural Christian roots and genuine Christianity.