Piedmont and Eubanks Welcome Center
If they're open, you have to stop at the Eubanks Welcome Center/Trail Office. Finally, there's a place for trail lovers to congregate, get trail information, & buy a souvenir trail t-shirt. And the people that work/volunteer at the center are incredibly helpful & friendly.
It's easy to find because it's right beside the trail, it has a clear sign, & there are usually a plethora of bikers gathered around outside.
I recommend you stop here, buy a t-shirt, make a donation, and chat with like-minded folks.