Go to the Clemson 4 Wheel Drive Center (Welcome To Clemson 4 Wheel Center
). Their shop is actually in Seneca, on Clemson Blvd. They do some good work... and Im sure they can hook you up with some group rides. Also... there used to be a club on campus called "Clemson Offroad". Look for them at the student orgs fair at the begining of the fall semester. If they're still around, Im sure you can find them.
For wheelin in that area, check out Rice Creek and Gulches ORV Park. And Uwharrie National Forest isn't too far away.