This link is to a Wired video showing the skimmer being installed. It also shows how people do and do not hide the keypad when they are entering the PIN.
http://www.wired.com/threatlevel/2010/09/skimming-video
For more information on debit/credit card skimming check this out:
http://blogs.techrepublic.com.com/five-tips/?p=299