Reserving a seat on JR train

If I want to reserve a seat on a JR train, what is the best way to say "I would like to reserve a seat" in Japanese?

Most ticket windows will understand you're trying to reserve a seat. I'm sure they'll understand that much in English. Just give them the date, train service and number, and from/to stations and they'll understand.

I second the previous answer. I never had a problem. Their English was much much better than my Japanese.
I wrote on a piece of paper the date of the trip, the departure town, arrival town and the possible time when I was planning to leave.

In a few cases I did it 30 minutes before departure..

very easy, no Japanese required to get a ticket fo seat on the trains. Just wait in, when you get to the front, just tell them where you want to go, they will show a list of times. very easy. no worries....have fun