The phone rings, you pick it up, and the caller identifies himself as an officer of the court. He says you failed to report for jury duty and that a warrant is out for your arrest. You say you never received a notice. To clear it up, the caller says he'll need some information for "verification purposes"-your birth date, social security number, maybe even a credit card number. This is when you should hang up the phone. It's a scam.
The FBI advisory on this recommends "Never give out personal information when you receive an unsolicited phone call".
I have occasionally received unsolicited calls from my bank. After the briefest of introductions, they normally ask me for my credentials in order to continue discussing whatever it is. It still perplexes me that they get all shirty with me when I insist on being given their credentials first - after all, it's them who called me. How do I know who's really on the line?
Snopes.com suggests a good idea: have the [alleged] bank person read out your details and agree or disagree with them. I doubt any decent bank would do this, and yet they are asking us to read out our details to them over the same phone line. Double standards? You bet.