I hike this mountain all the time. It is a great hike with some nice views on clear days.
Here are directions to the trailhead. Take 805 South and exit on H street east. Keep going east and you will cross route 125. H street turns into Proctor Valley Road. Take a left on Duncan Ranch Road. Find a place to park and do not worrry about your car as it is a residential neighborhood. Walk back to Proctor Valley road and take a left. Walk about 1/4 mile (approx) and look hard for a trail up and to your left. It can be hard to find because this initial part of the trail is covered by ground cover landscaping. This google map link shows the rest of the trail.
www.gmap-pedometer.com/?r=2537311
Happy Trails