Watch your money and belongings while in Italy, especially Rome and Florence.
The gypsies are en masse and very, very deft. Trust me on this.
Carry your money in your front pocket and hold tight to stuff, I would not wear a backpack. If you want, when in Rome and Florence in touristy areas you can usually spend a few to scan the crowd and you will see the gypsy kids working the crowd. Usually the pickpockets are more women, women w/babies, and kids.
When I was in Switzerland, I was told that was the only country in Europe that did not have gypsies in it. I believe them, the Swiss are like way paranoid.
Anyhow, they also like carbonated water over there so if you drink non-carbonated bottle water over here in the states make sure you get agua no gas or whatever the hell they may call it. Just keep on eye on that.
When in Munich MAKE SURE YOU GO TO HOFFBRAUHAUS. It is off the Maziplan (sp?) square (I think), totally awesome and kick butt place.
Also, I wouldn't worry about carrying too much cash, but then again I went before the Euro was out and used. Most credit cards actually give a pretty good exchange rate and are widely accepted and easy to use (except at the Eiffel Tower).
When eating out, do not tip. Well you could, but prices of the meal includes tip so unless you get really cool awesome service, gratuity is already included. Unless that has changed recently and I have never been to the UK so they may be different.
In Italy drink all the Chianti you can, and in Germany drink all the Beer you can. Usually cheaper than sodas and other drinks.
Have fun!!!