Visiting a Bierkeller in Franconia should be high on every visitor's list of things to do. It's a part of the culture unique to this part of the world. This is a ranking of personal favorites.
The 7 Brewery Trail or 7 Brauereienweg is one of the top beer hiking trails in not only Franconia, but likely the world. With six breweries and two top Bierkellers en route and some lovely rural scenery, you can't go wrong walking this great trail.
Griess Kellerbier is about as perfect a session drinking beer as you'll find, with a dry fruity palate and long slightly bitter finish.