Our flight arrives in Berlin at 7am and we need to be in Hamburg by mid-afternoon. What is the quickest, easiest and economical for our family of four. Is there time to explore Berlin at all or should we plan to return in another day? My husband and I have enjoyed Berlin on a previous trip but now that we're taking our college kids back I was wondering if the forum could make some recommendations of highlights upon your experiences.
Quickest and easiest will be a taxi from the airport to Berlin Hauptbahnhof, then a train to Hamburg (train time under two hours). That train will have discount fares if you book in advance for a specific train, but those tickets will have limitations on exchanges, so if you miss your train the ticket would be worthless. Depending on how risk-averse you are, you may want to chance it, if the cheap tickets are still left for your date of travel. If you don't want to chance it, you can buy tickets on arrival at the Hauptbahnhof.
To find trains, use the Bahn (German Rail) website http://reiseauskunft.bahn.de/bin/query.exe/en, following Rick's tutorial: http://www.ricksteves.com/travel-tips/transportation/trains/online-schedules
Be sure to put in 4 travelers and the ages; for the discount (Saver) fares, there's a further reduction for more than one traveling together. This way, you can see the price difference, and see if you feel that's worth the risk.
Just for fun, I picked the random date of September 10, 2015. For 4 people, the Saver fare was still available on most but not all runs. It was €49 for 4 adults - all together! The full fare for 4 adults is €312.
For that much of a price gap, I'd probably take a chance on the pre-booked ticket. And consider a seat reservation; these cost €4.50 per person, but mean that you will know where you are sitting, which is a great convenience after a long flight (no schlepping your bags through the train while your try to find seats together).
Thanks for the advice! It pays to plan ahead.