Narita Airport –> Tokyo Station –> Maihama Station
Haneda Airport –> Hamamatucho Station –> Tokyo Station –> Maihama Station
Shinjuku Station –> Tokyo Station –> Maihama Station
Yokohama Station –> Tokyo Station –> Maihama Station
Tokyo Station –> Maihama Station
You will find that most major train stations also have direct buses to Tokyo Disney Resort. I’m sure that you also noticed that most all of the above stations go into Tokyo. From Tokyo to Maihama you will be taking the Keiyo Line. It can be a long walk from some train lines, but there will be signs to direct you, even kindly telling the distance to the platform. If there are any other stations you’d like directions from, please comment below and I’ll be more than happy to add them to the above list.
From Maihama Station you can either take the Disney Resort Line Monorail or walk to the park of your choice. Maihama Station has two exits, but pretty much only one is used. To go Disneyland follow the crowd to the right and over the bridge. It’s very simple and quite obvious. DisneySea is a bit more of walk and can take at least 15 minutes. I would opt for the Monorail which will be on the left after leaving the train station exit.