It's very easy to plan your connections (and buy tickets) if you just go to www.bahn.de, and switch to English in the upper right corner where it says "Deutsch" As others have said, Frankfurt Airport has a long-distance train station, so in that regard is easier to get to, while in Munich you will have to transit to the suburban train (S-Bahn), which is underground from the platforms where your long distance train from Nurember will arrive. Frankfurt is definitely more straightforward. High-speed trains ("ICE") to both cities run pretty much every hour. Nuremberg is halfway between Frankfurt and Munich, so every train connecting the two cities stops there