You will not need to give us your credit card number to make a reservation for hotel rooms. We do ask, however, that you give us as much heads up as possible if you need to cancel or postpone your reservation for whatever reason. You can make a reservation by letter, phone, e-mail, IM, chat or twitter message.
You can pay us upon departing the hotel by cash or credit card (VISA or Mastercard). Of course cash is preferred and you will find that many small vendors and restaurants in Germany do not take credit cards.
You can check current exchange rates conveniently here.