Before starting your journey you will need to find out the train schedule, then visit the station or go there ten minutes before departure and then at the ticket office, Midori no Madoguchi, a counter symbolized by a green logo of a marked man in white sitting on a seat.
Here you can purchase both a “non-reserved” seat (you can sit where you want, if seats are available) or a reserved seat. The reserved seat is more expensive than non-reserved seat. Then you can proceed to the platform with your ticket. If you have a Japan Rail Pass, there is no need to buy a ticket or reserve your seat in advance (excluding peak periods), you can board non-reserved cars. If it is a peak period or busy train, you may need to travel standing in these areas, especially in the case of local trains but do not worry, this rarely happens. It is also quite possible to reserve a seat for free with the Japan Rail Pass at a Midori no Madoguchi.