The timetable will indicate if an advance seat reservation is required or recommended. You can make reservations either at a German train station or directly online, up to 3 months in advance.
More about seat reservations
Finding departure times at the station
At all German stations you will find timetables showing departure times and platform listings. At major stations in Germany, computerized boards offer up-to-the-minute departure information. You can also ask train staff for schedules at the ticket window.