How do you swipe your Oyster/metro/RFID card?
A quick tap directly over the reader
Slap, hold and twist as you pass through the barrier
Waft without making contact
I used to be a Wafter. However, when I started checking my Oyster balance online regularly, I discovered that the barriers would frequently open for me but fail to register one endpoint of my journey. After the umpteenth time of having to file for a refund from being hit with the maximum daily charge, I decided to change. So now I'm in the Slap-and-Hold camp.