Want to get the best service possible when you go out to eat? Put on a clean shirt. Also, be male. That’s the advice of researchers at the University of Missouri, who surveyed 222 current and former restaurant servers to learn what type of customers were expected to leave the best tips. Race didn’t matter all that much, although compared to white customers, well-dressed minorities were thought to be more likely to leave good tips, while casually dressed minorities were identified as more likely to leave poor tips. Well-dressed men of any race were identified as more likely to leave good tips compared to women, while casually dressed men were seen as the least likely of any group to leave good tips. And yes, the expectation of a good tip is more likely to encourage good service.