[dg7feq]

Hello,
you can buy a SIM-card in lots of shops in germany.
The mobile carriers have shops all around (T-Mobile, Vodafone, eplus, o2). There you can buy a card for about 20 Euro including 5-10 Euro of calling balance.
The calling tariffs are quite high if calling abroad (expect about 2$ a minute to USA).
for cheaper calls dial 0180-5151051 first, and then the international number (will be <1$/min, starting at dialtone...)

If you dont have a phone for the european frequencies it can be a option to buy the card with a cellphone in a starter-kit. In our local store they had T-Mobile SIM-cards with a Motorola cellphone for 15 euro last week! - you should always get a phone+prepaid-sim below 50 euro (remind that the phone would be locked to this sim-card).

When purchasing a sim-card you need your passport to register the card.

If you want a cheaper card you can go to a "ALDI" supermarket as Snaimon already suggested. This card needs to get activated on a hotline - i dont know if they speak english though. There you have a lot cheaper tariffs for inside germany but the same high tariffs to call abroad.

Chris