For some reason best left to psychiatrists, the trailhead is sometimes the most dangerous location of a hike. Along the Appalachian Trail, incidents involving hikers with robbers, murderers, and general creeps have historically been almost completely confined to those areas of the trail that cross roads.
        I'm not saying you should lose sleep about murderers, but take some precautions at trailheads, particularly in the east bay, where for some reason groups of people tend to hang out and drink beer at trailheads.

• Lock you car. Keep anything valuable or enticing to thieves at home.

• Don't linger at the trailhead. If you feel uncomfortable with the atmosphere at the trailhead, consider leaving to hike elsewhere. If you decide to stay, head out onto the trail; you can consult the map once you get going.

• Upon returning to your car, have your keys ready and be quick to get into your car.

• If you encounter suspicious or threatening people, report them to the management of the park. Park rangers are considered peace officers.

• Carry a cellular phone. A marginal tip, since cell phones won't get a signal in many places. I feel it can't hurt to carry one, and once I used mine when I left my car lights on and needed a jump.