Once you've ensured that you aren't using an obvious pin number for your ATM card, one step for extra security could be to write a fake pin number on the card.
Photo by Chad McDermott (Shutterstock).
Should the card ever get stolen, the criminal will probably try to use the number written on the card to withdraw your money. The trick is to write it in such a way that it's hard to read (difficult to parse eights and threes, for example). If you're lucky, they'll try three different incorrect PINs, which in most cases will lock out the card.
To be clear, if you know your card is stolen, you need to call and cancel it. But this is a nice extra layer of protection if you don't notice the theft right away.
LPT: Put a sticker with a fake PIN number on your debit card. Make the numbers hard to read. If you lose it and someone tries to use it (3+ times) the terminal will lock your account and eat the card. [Reddit]