I've hiked all three sections of the Billy Goat Trail numerous times, with groups of friends and with my teenage nephews.
Paid parking is available at the Visitor's Center. Free parking is available on the side of the road, by Old Angler's Inn. Park at your own (towing) risk at Old Angler's Inn.
If hiking section A, be prepared for a bit of rock scrambling, especially up a cliff face along Mather Gorge. During peak season, this section of the trail can get backlogged with people going up and coming down.
Hike section B or C if you want a less strenous activity.
I've hiked section C during a thunderstorm. The only thing I wish I had with me was a plastic cover for my backpack, where my camera was. Otherwise, there was something peaceful and zen about hiking in the pouring rain.
Wildlife seen in the area include turtles, Canadian geese, and a garden snake sunning on the rocks.
I highly recommend the Billy Goat Trail.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.