Excerpt from here.
1. After the telemarketer finishes speaking, propose  marriage to him/her.
 
2. Tell the telemarketer you are busy at the  moment, and ask him/her, to give you his/her home phone number and cell number  so you can call back maybe very late at night.
 
3. Keep asking the  telemarketer to tell you his spiel all over again. Do this several times.
  
4. If you receive a call during a meal, tell the telemarketer that it's  lunch time, but ask him/her to hold. Switch to loudspeaker mode and eat your  food in a languid noisy fashion, chomping away and continuing with the  conversation.
5. Tell the telemarketer that all business goes  through your representative, and hand the phone to your five-year-old.
  
6. Say that you are hard of hearing and that he/she needs to speak up  -- louder -- louder -- 
 
7. Tell the telemarketer to speak  really really slowly because you want to write every word down.
  
8. If the telemarketer starts off with "How are you today?", say "I'm so  glad you asked, because no one these days seems to care, and I have all these   problems...
 
9. Cry out in astonishment, "Rani, is that  you? I've been hoping you'd call! How is the family?" When he/she insists it's  not Rani, refuse to believe it and say, "Stop kidding me!" This works  especially well if the telemarketer is female.
 
10. Tell the  telemarketer to call at your office number and give him/her the number of a  rival telemarketing organisation instead!
 
