If you want a better relationship with the plumber, the electrician, or the cleaning service, don't just send a check or leave an envelope with cash. Include a simple thank-you note from time to time: "the house has a new and welcome silence now that the toilet doesn't hiss all day long. Thank you." The benefit? "We'll go out of our way for people who thank us for a job well-done," says the owner of a landscaping and lawn service in New York.