You can grab a somewhat detailed map of this network at Saucon Valley Bikes, it might help, it might confuse you. The map does not include all of the trails, but a good portion of them. Head out in any direction you want, there are a few road crossings and a few branches that just end at a road. There are a lot of trails in this area and you can make many different loops. Watch out for the frisbee golfers.
378 South into Bethlehem. Follow 378 until you see Puggy Dr. on your right, take this and loop around to the left as you cannot make the left at the light. After crossing the light you will be going up Mtn Dr. Take the road on the right across from the TV station (channel 39 PBS I believe) and park in the uppoer lot. There are trails all over.
http://www.singletracks.com/item.php?c=1&i=891