|I totally agree with #4 about keeping them going (but don't give them any info).|
My classic was an unsolicited phone call from some double glazing outfit.
I kept them going for ages, asking tom fool questions about U values and other technical details, that appeared to make them wriggle. Eventually it got to the bit about purchase and I simply said that I was very interested but unfortunately I was only baby sitting and live in rented accom. The call ended - think of the money I cost them LOL.
I have also found that speaking in broken English (any language that you can mimic) works well, or keep saying you are deaf and asking them to repeat what they are saying or speak louder.
The other one is to attempt to sell them something.
Always pop back and let us know the outcome - thanks