Originally Posted by
ppp909
With the JR pass, as has been said, you have to buy it outside Japan and activate it when you're there. It may not be relevant to you, but you don't have to activate it when you arrive. I was there for ten weeks with a three-week JR pass and used it somewhere in the middle.
Another tip that is often overlooked is that the start of the pass does not need to coincide with the date of exchange (although it usually does). You might want to, for example, turn in your exchange order and get the actual pass at the JR ticket office upon arrival in NRT, even though you might spend a few days in Tokyo and not want to have the 7-day validity start until the day that you leave Tokyo for points south (er, west). Just tell them the first date that you want the pass to be valid. This has several benefits, including allowing you to start your journey on the first day of validity at any JR station and not have to pay to get to a station that can do the pass exchange/activation (which are only major stations).