The map at the parking area had the best advice on the route to take, if you're up for the whole 1-mile hike (it said 1.2 miles, but it sure didn't feel that long). Not long after crossing the road and heading up the hill, take a right on the Appalachian Trail. Then take the second-left trail and follow the blue blazes (painted marks on the rocks, trees, etc). That saves the best for last--the 360-degree view at the top. But if you're just wanting to get in and out ASAP, just march straight up to the top and come back down the same way.
The view at the top is sensational. If you aren't up for doing Old Rag, this gives you a little taste of the experience while saving you about 4 miles of walking/hiking. In fact, I've hiked Old Rag with friends who, when they get to the rock scrambling, discover it freaks them out -- a surprise to everyone, themselves included. So, before trying Old Rag, Bearfence is probably a good test to ensure you don't have some undiscovered phobia! (Bearfence doesn't require jumping over any crevices like Old Rag -- but close enough.)
For those who have done Old Rag, this won't be nearly the exercise or experience -- except that when we went, there was almost no one there (on a Saturday afternoon even!), and it was great to sit at the top, just the two of us, and enjoy the serenity and scenery.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.