I've used my Nationwide card all over the world on every trip and never had a problem. I'd never go back to Travellers Cheques, too expensive and too much hassle.
The tip is to do exactly as you do at home which one would hope people do anyway, which is to check the cash machine for tampering and as per other post place one hand over the other to block any images being taken while your entering your pin.
I always use cash machines that are inside the banks whether at home or abroad as these are safer and less likely to have been tampered with. If I use an external machine I take the precautions as above and tend to pick well used machines in busy/open places as again these are less likely to have been tampered with if they're used frequently and in view of many people.
On another note many people seem worried about the machine swallowing your card and being stranded with no cash, again do as you do at home, take another card as back up and cash which can be kept in your safe for emergencies. I've only had this happen once before on Zante, we emailed the Nationwide the same evening to advise them and we used another card for the rest of the holiday whilst the swallowed card was cancelled.....just in case. Easy and no real hassle to us.