I just got another call from the 516 area code...

[gratuitous]

1. Another effective method

I ask, "What is your full name?" After about the fifth or sixth time, the caller usually just rings off. If I get some variation on "Thomas Jones," I'll ask the name of the business they're calling from, and where it is incorporated. One dimwit told me he was calling out of Walla Walla, Washington. I have a bookmark to the Washington State Corporation Division for work. I told him his company wasn't incorporated in Washington, and what was the REAL name of his outfit? After I've established that the caller isn't really Thomas Jones and he isn't really calling from where he says he's calling from, I then ask to speak to his manager. Invariably, the manager isn't there right now, so I ask for that person's full name.

I don't usually have to go beyond that, but I have other nosy questions just in case.