djm3 made an interesting suggestion. One excellent resource is the FRA site, www.frankfurt-airport.com for general info which will give you an overview of the Regional vs the Long Distance train systems that are both conveniently accessible from Terminal 1. Also, bus system is located in Terminal 1 as well although I personally prefer the trains. By the way, you can count on the trains being "on-time" there vs USA.

Have fun--------