There are several loop options with some blacktop used to link them. The one my son and I like the best is their 21 mile loop. It has a few very technical spots, but the majority of the trail system is awesome singletrack. The map is a bit difficult to make out at first because there are no trail names, just numbers. They do list the trails according to beginner, advanced or expert. You can make sooo many different loops you can ride all day and not feel like you hit any trail twice. The 21 mile loop puts you on nearly every trail in the park, (nearly). Also, check out Coopers Rock State Park just west of here toward Morgantown. Great riding there as well.
Exit off I-68 east of Morgantown WV at the Hazelton exit and go south a few miles to Big Bear Lake. This is a private resort area, however bikers are welcome. Cost is $5.00 per day or if you ride there often you can obtain a season pass. A waiver has to be signed and a trail map is provided at that time. There are several suggested rides with something for all abilities. Check their website for open dates. They close during hunting seasons.
http://www.singletracks.com/item.php?c=1&i=2432