Train/Subway system

How difficult will it be to get around on the train/subway system? I'm pretty good at navigating, so I'm planning to tour around Japan by myself instead of booking a tour. Is this a good idea? 

The train/subway isn't hard to navigate once you get the hang of it. There are signs in English and the subway stations (at least in Tokyo) are numbered according to the train line.

You can buy a prepaid card, called SUICA or PASMO at any large station in Tokyo, and charge money on it so you don't have to keep on going to the ticket machine every time. Though, keep in mind that there’s a different prepaid card system for each region, so if for example you go to Kyoto or Osaka, the prepaid card for Tokyo won't work there.