The best way is first to fly into Frankfurt (FRA) or Munich (MUC) airport. Frankfurt has more air connections, but Munich is closer to the venue.
From Frankfurt airport railway station you can train to Stuttgart and from there the regional train to Aalen and another one from there to Nördllingen. Total train travel time is around 3h 20 minutes.
From Munich Airport (München Flughafen) you can take the suburban train to München-Pasing or Munich Central Station (Hauptbahnhof (Hbf)) and from there to Nördlingen with usually changes in Augsburg and/or Donauwörth.
An excellent website for travel enquiries is available at the Germain railway website, in 8 different languages. You can also buy tickers at this site, as at vending machines on railway stations. Please note that you cannot buy tickets from conductors and boarding trains without a valid ticket is regarded as fare-dodging and leads to hefty fines.
If you plan to travel to the venue by way of your own car, please note there is no parking at the Klösterle Hotel. You will have to use the subterranean garage (EUR 8,- for 24 hours) or the free parking lot at “Kaiserwiese” outside the city wall.
For JUFA, there is a nearby parking lot.