Writing this after having been to Japan, I feel silly writing this post but I know others may have the same questions I had when using my PASMO or Suica card. Japan Guide has good information on how to obtain these cards and where you can use them.
We used the PASMO card and we loved the convenience of it. We knew we would be traveling a lot throughout Tokyo, and the PASMO is accepted on all railways within Tokyo so we initially loaded it with ¥4,000 per card, and was able to get around for 1.5 weeks (including our train ride from Narita to Nakano which cost ¥1,000 via Keisei Rapid Line Express).
We purchased the PASMO card once we arrived at Narita before we hopped onto the Keisei Rapid Line Express. When you get to the automated ticketing machine, there is a button for "English"- make sure you press this first before you begin pressing any other button. Each person in your party will need their own card.
1. As you approach the gate, you "tap" your PASMO or Suica card on the round blue highlighted "IC" screen
2. The automated gates will open in front of you, and as you pass, you can see your balance remaining (¥820)
Here is someone going through the gates with either his PASMO or Suica card.
How do I know my card balance?
Note: Your PASMO or Suica card won't be deducted at the departing train station; it will be deducted at the arriving train station. For instance, to go from Shinjuku station to Tokyo station, it will cost you ¥190 one way. As you "tap" your PASMO or Suica card at Shinjuku (departing) station, the card is just "accepting" your initial departure station. As you exit Tokyo station, you will "tap" your card again and this 2nd "tap" is when your card will be deducted the ¥190 (arriving station). You can also see your card balance at the automated machines (the same place where you can load more ¥ onto your card).
Tip: When you first purchase your card, the card will automatically add a ¥500 "card fee" which is fully refundable at the end of your trip. Thus, when we first put ¥4,000 on our PASMO card, only ¥3,500 was available for traveling since the initial ¥500 was for the "card fee". We were able to get our ¥500 refund at the train station once we got to Narita airport for our departure flight.