What are some "must-see" trips while be based in Nuremberg (and using train).

Bamberg. Beautiful, unique beer, scenic hill beer garden, and easy train ride.

Bamberg. Beautiful, unique beer, scenic hill beer garden, and easy train ride.

Besides Nuremberg, there are tons of interesting places to see. With a VGN Tagesticket plus, it is also cheap to travel by public transportation.
Rick's fave, Rothenburg ob der Tauber.
Bamberg
Graefenberg and the brewery trail.
Bayreuth (you a music lover? Wagner HQ)

Munich , Neuschanstein (the castles). i would also add in Salzburg , which is a long day . One option we've done is to do an overnight at a place which could be a day trio if it would be an esp long day. We get an inexpensive hotel or pension, carry just a change of underwear and a tee shirt and leave the main stuff in our hotel base.

Having lived in Nuremberg for about 3 years a very long time ago, my advice would be to be sure to explore that lovely city itself. This link goes to the official city tourism portal in English. I hope you find it useful.

Noerdlingen - basically Rothenburg without the hordes of tourists.

Don't make plans until you check the time it will take to reach some of these places - some of the suggestions above will require substantial round-trip train time. Below are the fastest options round trip from Nuremberg.

A town too far?
Nördlingen: 4
Neuschwanstein: 7.5
Salzburg: 6.5

More reasonable day trip options:
Rothenburg: 2.5
Bamberg: 1.5
Bayreuth: 2

Some additional places within a reasonable distance:
Würzburg: 2.5
Regensburg: 2
Iphofen: 1.5
Bad Windsheim: 2

The VGN Tagesticket Plus that Sam mentions covers day trips to all of the last 7 places I named except Würzburg and Regensburg: Use the BAYERN TICKET for these. Both the Bayern Ticket and VGN day passes can be bought at the station on the day of travel and require use of regional trains (no high-speed, long-distance trains like the IC, ICE, EC or RJ.)

Of course Nuremberg is a good place too. Here's a guide to walking the city.

If you'll have access to a car (which I suspect you will if visiting a soldier), take a drive into the Franconian Switzerland region immediately to the NE of Nürnberg. It's filled with scenic rock formations, nice old villages and castles.

Give Coburg a look. It has (in my opinion) the best castle in Germany.

Graefenberg, which I mentioned previously, is in the Franconian Switzerland, as it is called or Fraenkische Schweiz. It is the home of the Funf Seidl Weg, Five Mug Trail. Five small breweries along a 6-mile trail. So if light hiking and beer appeal to you, this is the ticket.

Graefenberg is reached from Nuremberg Northeast station, which is not connected to Nuremberg main station. Get there on the U-Bahn.