We have never hosted a student, but several people at church have. So far all experiences have been good. Some have even gone to meet the student's family. They are well screened and will be interested in experiencing America.
Have a list of activities, places to go, things to see etc that you can do as a family or the student can do on his own. Encourage him to participate in clubs and activities at school and in the community. Most of them are looking for "local flavor" and experiences, so here is your chance to spread your wings a bit, too.