The friend we will visit in Berlin suggested we take a side trip to Madrid or Prague. What would be the best transportation..train or plane? Should the tickets be bought here in the USA or wait until we get to Germany? We will only be going for the weekend so time is somewhat of a factor. Any tips or suggestions on what choice to make for the city?

Well, I would definitely do Prague instead of Madrid if its' only for the weekend. Prague is much closer and you wouldn't spend half your time traveling. Also, it's a fantastic city with tons to see/do and very inexpensive vs western europe.

prague is the place...easy train connections....also another side trip is dresden...often overlooked but fantastic...

I would also suggest going to Praque. Of the two cities, that is the one that got under my skin. You can take a train from Berlin Zoologische Garden station. The trip takes approx 5 hours and please remember to book a seat when you purchase your ticket or you could find yourself standing the whole way!

If you took a train to Madrid by the time you gotr there it would be time to come back! For Madrid in that short a period you would have to go by air. Prague, as others have stated is about 5 1/2 hours from Berlin (no changes) by train.

Prague. Buy the tickets when you get there. (train is easiest & cheap)

"Buy the tickets when you get there."

I was wondering about where to buy the ticket with the situation with the Euro now. I thought possibly the ticket would be cheaper in the USA. I don't know anything about the Rail Passes. Would one trip make a pass worth while?

I can't think of any single trip that would make a pass worthwhile.

This is not my idea of a "side trip". Would you plan on staying in New York for a week and make a "sidetrip to Los Angeles"?

Leipzig or Dresden are good day trips from Berlin. As is Spreewald. Although for the weekend, I suppose, Prague could be OK.