If the trails that aren't signposted were signposted, they would be ruined within a few months. It's better this way, honest! It's a long story... Si can tell you sometime

Follow your nose, ride the steepest rockiest stuff you can (it drains better) and you'll have learnt your way around in no time. The Transpennine trail (big fireroad at the bottom that runs parallel to the railway) means you can never get truly lost, if you keep riding downhill you will get to that eventually, and it's signposted).
The maps here are pretty helpful though
http://www.wharncliffe.info/maps.html