I must say, that although I was never a JW, I found the best way to get them to stop coming to my door.
Many years ago while living with my mother some JWs came to the door. I was very polite at first, giving them the "I am happy with my religion" and "I don't want to join a cult". They would not give up.
I showed the woman my pentacle (equivalant to a cross for us witches) and told her that I had found the true path for my life and I was sorry that she didn't understand that other people could find truth in religions different than hers, and that I truly hoped that one day she could open her mind to the possibility that others had the right to not be disturbed by people "pushing" their religion down the throats of others.
She tried very hard and wanted me to come to a meeting and I told her no. When she continued to push I told her that coming on the sunday would interupt my ritual killing time, a look of horror came over her face and she nearly fell down the stairs trying to get away!
My next door neighbour (a stout catholic) was killing himself laughing! He knew I was doing it to get rid of her and when she came to see him he spoke only in Italian to her (He spoke english just fine btw) so she left him alone.
They have never returned to my mother's house to witness there, and we don't even own it anymore!