There are many ways to top up the cards, but for me, I do it at home.
This is the equipment that I use to top up my card.
It's called a Felica Reader by Sony.

I think it's the most convenient way to top up and you can gain credit card points too (from your bank).
The public transport in Singapore use a RFID card. Do your country also have something similar?
I know Hong Kong, Bangkok, Malaysia have RFID payment cards too.
Click here to view how a EZLink card in Singapore looks like.
Those in Singapore, how do you always top up your EZLink card? Giro? The GTM Machines at MRT Stations? or Transitlink kiosk at bus stations? Or like me, using your own Felica Reader?