Lisa,
Since you're posting, I'm guessing that you're okay from the earthquake and tsunami?
The security chief told us that the best way to use plastic is to use all cards as if they are credit because in most cases, you must sign the receipt. That gives you and the merchant a little extra protection, especially if the merchant does "due dilligence" (an IRS phrase) and verifies the ID.
We changed banks a year ago because our business account got hacked TWICE in less than 6 months. Once was something like 4 car stereos that had been ordered from Europe and were to have been delivered to the store - the address was changed just before they were shipped. The second time was a real mess - it was one of those Nigerian scams. Wound up being thousands of dollars of UPS overnight charges because they set up a UPS account in Los Angeles with OUR information. We had phone calls from all over the country and even visits from the local PD and sheriff because of it. It was crazy!
Sometimes the best way to protect yourself from credit card fraud is to watch your account CAREFULLY and question ANYTHING that looks odd. Mike checks our bank information every morning and if anything looks odd, he asks me and if I don't know, he's on it to find out what it is. Most of the time, it is legitimate, but his vigilance has caught the bad ones before they became disasters.
If someone has written CID on their card and hasn't signed it, I use my judgement. I usually give them my "I got a 15 minute lecture from the Post Office because all I had on my card was CID". Sometimes, it's because the signature's worn off and other times, they are acting on the old information of "don't sign your card". Usually, they will sign the card then - which I'll match with the signature on their ID. Sometimes they'll say "I'm not signing my card anyway. If that happens, I'll usually give their ID a VERY careful check while telling them that if the card isn't signed, they don't have any protection if it is stolen.
I haven't turned a card down, but I'll usually tell them, "If you bounce a charge on me, I'll have you blacklisted on every bead store in the country". They usually look horrified and say something like, "I'd rather go to jail!" <LOL>
MY POS (point of sale) program has a function to accept debit or credit cards. If it's a credit card, I would have to input the number and have them sign the receipt. Since I've already swiped the card on my card reader and I don't want to have the card information on my computer, I use the debit function, which doesn't require a number to complete the transaction. I don't want any information on anything that can be hacked.
My advice would be to go with your gut feelings. If you get a "hinky" feeling about a transaction - don't do it - or do everything possible to protect yourself. You can always ask to see a second ID. I would make a joke about it - "gee - this card doesn't look like you. Do you have one that does?" Anything to lighten it up. Most people understand - I've had very few people get huffy because I asked them for ID. IF you are worried about the card being fake or stolen - VERY ELABORATELY and DELIBERATELY - look at EVERYTHING ON THE CARD and comment about it. "Oh, my sister lives a couple of blocks from you" or "When did you get your hair dyed?" It lets a crook know that you are paying attention to details and CAN identify them if you had to. If you ask with a smile and a joke a non-crook will just think you're crazy! <LOL> ("Crazy" is my trademark!)
Deb