Do I need to make reservations for some trains?
Most domestic German trains do not require a reservation. However certain trains do including the City Night Line night train. Reservation is recommended for the ICE high-speed train during busy times.
To check if a specific train requires reservation, you can look up the train in the timetable. The schedules indicate if reservation is required or advised.
You can make seat reservations up to 3 months in advance. Read more about seat reservations.