In Prague, Pilsner Urquell was cheaper than Coca-Cola when I was there a few years ago, so that was an easy choice.
When you're over there, be careful of pickpockets, especially in tourist areas of Prague. I wasn't a victim, but I saw people that were.
Read guidebooks before you go, and decide how much time you want to spend on things like museums. There are some great museums in Berlin, but they're not all for everybody. The former Reichstag is now a museum, that one was interesting and didn't take several hours to see.
There's a museum at Checkpoint Charlie which was interesting - it tells stories of how people crossed illegally from East to West Berlin.
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If you plan on going to museums, check for their hours ahead of time, some are closed on certain days, and some will have discounts at times.
Guidebooks and the Internet will also give you good ideas for restaurants before you go. You can match up places to your tastes and budget.