One of the first things you will need to do when planning your trip to Germany is convert your national currency to the Euro. To do this you can either get it prior to your departure at your local bank, or get it at the arrival airport in Germany at a currency conversion table. When converting currency at the airport table keep in mind that most are not open 24/7. Do not be surprised if the denomination of your converted currency is much less than that of your local currency. In recent years the Euro has been doing extremely well.
Another way to get Euro while in Germany is to use your ATM card. You can find an ATM at any bank. Most accept foreign ATM cards but not all. If your ATM card is rejected you will probably get a ?card not in network? prompt on the screen. You can expect a foreign ATM charge of anywhere from 2 to 4 dollars, depending on your card provider, per transaction.
Do not be totally dependant on your foreign credit card. A lot of businesses in Germany do accept American/British/etc. credit cards but not near as many as in your local Country, for example, VISA is accepted in most gas stations but only a few restaurants. It is a good idea to take Euro cash along anytime you go on the economy in Germany. Some American based companies/restaurants take U.S. Dollars, for example, all McDonalds in Germany take American Dollars.
If you plan well and spend your money wisely Germany will prove to be a GREAT vacation experience. If you are planning a trip to Germany, Great choice and have a great time!