Go to a Japan Rail ticket office, which can be found at any large- or mid-size station. Small stations may not have ticket offices.
Ask for someone who speaks English if you do not speak Japanese.
Tell the ticket agent where you would like to go and when you would like to go. If you know the exact train, provide that information. Otherwise, the ticket agent will tell you which trains go to your destination on your departure day and time.
Pay and collect your tickets. For express or Shinkansen (bullet-train) service between two cities, you will get multiple tickets for each leg of the trip. You will need all of these. One ticket represents the fare between the two points, and the other represents a separate fee for use of the express train. This second ticket also will have your seat assignment.