You want the Narita Express or Haruka (Osaka/Kyoto) included in your travel days. When to Skip It (Buy Single Tickets Instead)
If you are mostly staying in Tokyo or Osaka and doing local day trips, the pass is a waste of money. when to buy jr pass
The fastest bullet trains require an extra "supplemental" fee even with the pass; individual tickets let you book these directly. Pro-Tips for Timing You want the Narita Express or Haruka (Osaka/Kyoto)
Buying from the official JR site allows you to book seats online for free before you even arrive in Japan. when to buy jr pass