Adopt a need-to-know policy

Your bank and credit card companies will need to know information like your social security number or your mother's maiden name to verify your identity. Someone calling from one of these companies, however, doesn't need to ask you for information that is already on file, warns the Department of Justice.

The Justice Department likewise cautions against printing too much personal information, such as social security numbers, on personal checks. Think about how vulnerable you're making yourself just by writing a check.