Backpacking the Appalachian Trail?

Me and a friend of mine are going to be backpacking part of the Appalachian Trail. We will be taking the train to Harper's Ferry Wv. From there I'm not very sure. Would we be better off hiking North or South on the trail? Is there any good loops we could do? Also is there anything else I should know about this area? I have been backpacking before but never on the Appalachian trail. Is there any bon-fire restrictions, good shelters to stop at, places to get water? Any tips help! I will be there for a little under a week.