The technique that I use is to place my left hand directly on top of the keypad. I slide my right hand underneath and find the first two digits automatically, like touch typing. It doesn't matter how close someone is to me, they can't see the numbers being entered. Even if it's 2am in the morning and there is nobody around, you still need to cover your pin in case the machine has been skimmed and there is a camera set up to capture pins.