I am flying in and out of Frankfurt this summer, but need to take my bike on the train to Ghent and from Amsterdam. I have not been able to figure out how I can accomplish this from the DB Bahn site. My hope was to take my bike in a box and leave the box in Frankfurt, and to leave my bike assembled (minus wheels if necessary). Any help is much appreciated.
The German Rail website will give you some of that information. Click on details for each connection. From what I can see, major trains (ICD, ICE, Thalys do not allow bicycles), but a lot of regional trains do. I think you might be able to take a bicycle on board a major train in a box and store it at the end of the car with big luggage. I don't know if they still consider it a bicycle or luggage.
There is a box at the bottom of the page to check for trains that allow bicycles with a reservation for a fee, but that might only work for trains in Germany.
Deutsche Bahn's Intercity, Eurocity and regional trains have special bicycle cars, typically at the front and/or at the end of the train. Check the car position indicator at the platform. You have to buy a (cheap) bicycle ticked. Luggage storage on all highspeed trains (ICE, Thalys, TGV etc,) is limited, doors are narrow and stops are short. Hence the restrictions on bicycles. But you can disassemble any bike to a relatively small package:
http://www.bikequarterly.com/images/BQ_rinko.pdf.
http://velo-orange.blogspot.de/2006/08/rinko.html
To unfasten headset and pedals you need a headset tool and a 15mm spanner. If you do it frequently, e.g. for transport by car or storage at home, google "rinko headest" and "MKS Ezy pedal", which you can take off without (special) tools.