We fly into Frankfurt, have 3 days in Stuttgart, then a week in Berlin. We fly outfrom Frankfurt. Any suggestions on the best way to do the RT from Frankfurt to Berlin?
Take the train. Special fares for either the night train or day trains start at 29 EUR. See the timetables and prices at www.bahn.de. Click on "Internat.Guests" to view the site in English.
There are three sources for this route: airberlin.com, lufthansa.com and bahn.de (select International Guests on the top menue). Flights on Air Berlin from Tegel to FRA start from €29 one-way, are operated by Boeing 737s with tight seats, typical low cost. But reliable, cheap, save. Lufthansa use wide-body Airbus A300 on this 1 hour flight which is more comfortable than on Air Berlin's squeezed in seats. Roundtrips start from €99 (consider booking a roundtrip with just forgetting about the return flight). Most comfortable, roomy is the ICE high speed train. It also starts from €29 if you book online and in advace. Journey time is 4 1/2 hours though. If you haven't been to Frankfurt make sure you stay at least for a day as there are so many beautiful sights in the city and its surroundings.