Follow the arrows as it is a one way loop. Be prepared for some up and downs and loose gravel. You ride on the rim of the lake for a good portion of the trail, on somegreat singletrack. Watch out for the Yuccas in the flats and the cacti on the declines.
From Hwy 84 south take a left on to FM1730, there is a Texaco station on your right, and a sighn pointing you to Buffalo Springs Lake and Ransom Canyon on your left, you stay on that road til you see the park entrance on your right. They will charge you $3 per person and give you directions to the trail inside the park.
http://www.singletracks.com/item.php?c=1&i=1321