Before the "Do-Not-Call" list, I used to pretend like I really wanted what they were selling and ask to please tell me more. Then I would ask questions about it, again telling them that it sounds like a great product/opportunity. Finally, I would order a very large amount of the product ie: 600 cases of vitamins. When the credit card was requested, I'd say "hold on, let me go get it". Then I'd set the phone down and for 10 minutes, come back and read off 4 numbers, stop and say "wait, this card's expired. Let me get my other card." Set the phone down and walk away. They're more likely to wait if they think they got a "live one", thus wasting much more of their time.