Free From Broke wrote about his recent experience with small-scale credit card fraud. He had eaten at a restaurant and left a cash tip. When he got his credit card statement, he compared the charges to his receipts (yep, he saved them) and noticed that the restaurant had overcharged him. Apparently, the waiter had added an additional tip in the tip line of the bill. He called American Express and they promptly reversed the overcharge.
The same thing happened to me a couple of years ago. I, too, kept the receipt, which made it much easier to resolve the problem.
Lately, however, I've not been as careful about saving my receipts. As a result, I don't really know whether or not I've been a victim of a criminal waiter or not. I suppose I could start saving my paper receipts again, but Free From Broke has a better idea — take a photo of all your credit card receipts with your cell phone as soon as you get them. That way, you'll have a dated record of all your credit card purchases that you can refer to when you go over your credit card statements. If you have a free account with Evernote (a fantastic online service that lets you save, organize, and
search virtually any kind of digital information you throw at it), you can take photos with your phone and save them there.
If taking photos is too much of a hassle, you can use a geeky "checksum" method, which involves adding or subtracting a few cents to your tip in such a way that the total charge can be "summed" and "checked" to determine whether or not you were overcharged. Punny Money has a clearly-written tutorial on how to use the checksum system. If you have an iPhone, you can even purchase an application called Sudobility that does the math for you.