Attractiveness is positively correlated with tips for waitresses. I don't have a hyperlink to my freshman year psych textbook, but it's also correlated with getting hired and not being found criminally insane. I'm going to go evo-psych on you all and suggest that this isn't just a male desire to be surrounded by attractive women. Attractiveness is correlated with current health and childhood health, both of which are correlated with intelligence.
How can you make this work for you? Dress nicely. Wash. Make sure your hair is clean (although a friend tells me that super long hair is unprofessional for women). Plastic surgery is probably overkill.
Don't go too far though. Especially for women applying for knowledge jobs, looking too beautiful or sexual makes you look unprofessional, 'cause really, you can't be both hot and smart. That's just not right.