From Narita airport - around 70KM from the city centre - you can get a train to Tokyo, which takes around 50 minutes, and once there, a combination of trains and underground services are available to get you around.
Various different companies operate the different train services, and it can be confusing, but in truth you only need to use them for getting between districts of the city, because within Roppongi, or Shijuku, you can get around quite easily on foot.
Buses are comfortable but get caught up in the traffic, and it can take a while to get from place to place, and taxis are very expensive.
There is no point in hiring a car in Tokyo itself, but they are handy for getting out of the city to attractions nearby, such as Disneyland, although trains serve that too.
