Does the JR Pass cover Tokyo subways?

No. The JR Pass only covers JR-branded lines. It will work on the Yamanote line in Tokyo, but not on Tokyo Metro or Toei Subway lines.

Can I use the Nozomi Shinkansen?

Yes, but you must pay a significant additional surcharge. The standard JR Pass does not cover the Nozomi or Mizuho express trains without an extra fee.

Should I buy the pass before I leave home?

Yes. You must purchase an Exchange Order online or through an agent before arriving in Japan. You cannot buy the actual JR Pass after you have entered the country.

Making Your JR Pass Worth the Cost

Only buy a JR Pass if your combined one-way Shinkansen tickets exceed the cost of the pass. You must calculate your specific route costs on a tool like Navitime before purchasing, as recent price hikes make the pass a loss for simple round-trips like Tokyo-Kyoto.

Calculate your route cost. Use the 'Japan Transit Planner' by Navitime or Google Maps. Add up the individual cost of every JR train segment you plan to take. If the total is less than the current JR Pass price (roughly 50,000 JPY for 7 days), do not buy the pass.
Activate at a station. Once you land, take your Exchange Order to a JR ticket office (Midori-no-madoguchi) or a ticket machine with a passport scanner. You must designate a start date within 30 days of exchange.
Book seat reservations. While you can board non-reserved cars for free, use the JR-West Online Train Reservation site or station machines to reserve seats at no extra cost to guarantee your spot on long-distance legs.
Master the gates. Do not use the standard touch-style IC card gates (Suica/Pasmo). You must put your JR Pass into the physical slot of the manned gate or the specific pass-enabled automated gates.

Does the JR Pass cover Tokyo subways?: No. The JR Pass only covers JR-branded lines. It will work on the Yamanote line in Tokyo, but not on Tokyo Metro or Toei Subway lines.
Can I use the Nozomi Shinkansen?: Yes, but you must pay a significant additional surcharge. The standard JR Pass does not cover the Nozomi or Mizuho express trains without an extra fee.
Should I buy the pass before I leave home?: Yes. You must purchase an Exchange Order online or through an agent before arriving in Japan. You cannot buy the actual JR Pass after you have entered the country.