When prompted, stick your credit/atm card in the reader but don’t pull it out. WAIT. After about five seconds, assuming there’s nothing wrong with the card itself, you’ll get a message saying “Please remove your card.” At that point, remove the card and you should get asked for your ZIP/PIN as usual.

This trick has never once failed me, and it’s much faster & more reliable than jiggling the card a bunch of different ways to get the damn thing to read.

(Taken from Reddit)