Okay - as I said before: each reservation is 5 DM for one way (this means if you have to change trains, you get the reservation for both trains for 5 DM). Normally you have to do the reservations at least one day before, but there are now as well reservations possible until shortly before the train is leaving. Very often it is not worth to make reservations especially during the day. You can only make rservations for long distance trains, but not for the regional short distance trains.
Concerning the railway stations at the airport: There are two: one for the short distance trains (called Regionalbahnen )and the underground trains (called S-Bahn, they are indicated aus a white S one a green circle) to Frankfurt city and then there is a very new one for the long distance trains like the ICE, IC and EC.
The first mentioned railway station is directly in the basement of the airport (completely underground). Since I have never walked to the other one so far, I'm not sure how to get there, but I'm sure that there is a pedestrians lane to it.
But check the trains schedule before to check where the train is really leaving. There should be schedules posted at the airport - otherwise just ask.
Depending on which of the connections your are taking it is possible that you have to take the S-Bahn to Frankfurt Main Station (Hauptbahnhof, Hbf) and then the final train from there. It is a very big railway staion with at least 20 tracks - quite busy as well.
Hope this helps.
Have fun in Germany!
Just checked your post again: the Hbf is definitely not across the street because it is located rigth in the middle of Frankfurt downtown. But you are still rigth about the two railway stations though....
[This message has been edited by Blond Girl (edited 11-10-2001).]