There are 5 major trail loops, but all have trails that interconnect. I've ridden here many times and can say that I've never done the exact same thing yet. There is about 80 miles worth of total trails. A lot of singletrack, some farmers fields, some dirt/fire road trails. Excellent place to ride. Go here with lots of time!
In Cecil County, exit 100 off Interstate 95 North toward Rising Sun on Route 272 North. Take a right on Rt. 273 and follow to the intersection of Rt. 273 and 213, proceed through the traffic light. Fair Hill entrance to fairgrounds, race barns, Walls Hall and riding stables is 300 yards on the right. Immediately on your left is a parking area that connects with the Orange Trail. Parking is on an honor system of $2 a vehicle. There are 5 main parking areas, this is the easiest one to get too.
http://www.singletracks.com/item.php?c=1&i=1067