I think the best way to ride the trails is to just ride around them and explore until you get familiar with them. There really isn't enough space to get lost too badly. It is pretty good singletrack riding and is good for all levels of riders. If you get bored of these trails, you can ride over to the Summit Ridge area for more fun.
Driving north on 169 from Black Diamond turn right on 276th. Follow the road until you come to a water tower. Make a right onto the road across the street from the water tower (253rd Pl.). Go past 279th Pl. and you can hop onto the trails on the left.
http://www.singletracks.com/item.php?c=1&i=6170