Up The Old Chutes Trail to Barham Ridge Trail, to Anaheim Hills Trail down the hill to the right. This will take you to the Weir Canyon trail head.
Trailhead coordinates are, N 33.74739 degrees, W 117.58344, or look for the Maple Springs Visitor Center, 31330 Silverado Canyon Rd, Silverado, CA 92676
http://www.singletracks.com/item.php?c=1&i=7714