I just simply don't answer the door for them anymore. My dad told me once that he did for two men, one older and the other younger, and after he told them he wasn't interested the older man said he'd go to hell. On a slightly related note, I was at a bus stop with an older man once and a female JW came over and asked if we'd be interested in some reading material on the Bible and the man started quoting from it. This made her face light up and so she held out what was in her hand, which was a copy of The Watchtower. He looked at it, then looked at her and said, "Oh, you're one of those Jehovah's nitwits."
"In three words I can sum up everything about life: it goes on."- Robert Frost