An aging Indian* finding himself incapable of physically expressing his love for his wife visited the medicine man.
"Yes, I can help you," said the medicine man. And then he proceeded to administer his medicines and chant his chants. When he was done, he gave the man the following instructions: "When you need things to work, simply say, 'One two three.' And then when you're ready to be done, say, 'One two three four,' and you'll be done."
So the man went home to his wife, gave her a big kiss, and cheerfully said, "One two three!"
His wife frowned and asked, "What's the one two three for?"
Moral of the story: Never end a sentence with a preposition, lest you end up with a dangling participle.
*I'm not sure why it needs to be an Indian, but she got this joke from Star Valley, Wyoming, so perhaps that explains it.