You can never be too careful. Modern day conveniences have made our life much simpler. But you have to be very careful when using your credit card. The latest scheme to steal not only your money but your information employs the use of what are called skimmers.
Ingenico, a credit card manufacturer, has a guide on how to detect a skimmer that may be lurking in their terminals (Ingenico iSC250). Scroll down to learn more. A skimming terminal will be much larger than normal (wider and longer).