From the Trading Post, head East down the open field and cross the creek at the bottom. Join up with the 4 wheeler trail headed up the hill. Break right at the first trail past the swings and start up the steeper climbers trail. Very shortly you'll come to another cross trail, if you look to your right you'll see a nice wooden sign that says Magoo Rock. Just follow the arrow straight up the hill and you'll end up at the base of Magoo.