Originally Posted by
ND76
if you ride into the city on the Keisei Skyliner, this service terminates at "Keisei Ueno", which is a separate building about 1/4 mile from the main Ueno station. The Tokyo municipal tourist bureau operates a really nice information counter there; there are at least two decent sized guides on glossy paper that you can get in English that have detailed city maps of central Tokyo, including information on the two different subway companies (Tokyo Metro and Toei Subway) as well as the above-ground trains such as the Yamanote line. The Keisei Ueno station offers a covered connection to the Tokyo Metro (it is about a 1/4 mile walk to the actual subway platform on the Ginza line).
I'd take the Skyliner to Nippori and transfer direct to JR (Yamanote, Joban, Keihin-Tohoku lines). Nippori is both a JR and a Keisei station.
It's important to know where exactly you're headed in Tokyo; your destination often determines which mode of transport and which line to ride. Many destinations can be reached by both subway (Tokyo Metro & Toei) and rail (JR and private lines), but there are places (Roppongi for example) where it's only subway and other places where it's faster to ride JR there than the subway lines.
If you don't plan to hop around enough to justify the subway day pass, pick up a Suica card (contactless payment system) via machine or ticket office (midori-no-madoguchi) at most JR Stations if you're already in Tokyo. Or if you're flying into NRT, you can pick up a combo Ne'X/Suica (Narita Express) package that gives you a substantial discount on your ride into town and a Suica with Y1500 on it ready to use. You can add money to the Suica as you go and then use it to purchase a Skyliner ticket to return to NRT. The Suica works with practically all modes of transportation as well as convenience stores and McDonalds.