I am scheduled to land at Frankfurt am Main airport on Tues. April 17th at 07:10 (one checked bag). I would like to travel by train to Berlin as quickly as possible. There seems to be trains every 10 to 15 minutes. Any idea how long it will take me to get on board after I land? (I will need a few minutes to hit an ATM. ) Is it easy to do, and recommended, that I purchase the ticket online at the DB site before I leave or wait until I arrive? If I purchase on line can I use any train on that route? Would I need to check in and get a ticket or just validate something from the internet and get on? Fare currently is about 108 Euro. Is there anything better I should look for (I will just be going one -way)? And finally, is there a smaller town that I should take a stop over for a few hours enroute to Berlin.