I'm going to answer about men, because I feel more qualified to talk about them.
Hair dye: don't like it. I have a thing for graying hair. I wouldn't advocate that young men use gray hair dye, though, because that just looks weird >_>
Styling: I like it when guys go and get a good haircut about once or twice a year--not super-short, though, I've screamed when I saw guys who cut their girlish locks off. Fewer haircuts than that and it's a bit grungy; more than that and you never get to see a guy with his hair grown out a little.
Dudes with makeup: unless you're covering up a black eye or doing something really spectacular and odd, I don't want to see it. Before anyone screams gender discrimination, this is generally my standard for women too.
Plastic surgery: unless you need it and you're having quality-of-life problems, forget it. Fixing a severe underbite = good. Nose jobs = I'd be happier if you went and got it broken a couple of times (not intentionally, duh). Then your face would have some character.
Clothing: clothing is good. In general, I figure one should buy what one wants and wear it. I have styles that I prefer, just as I do for all of these aesthetic things, but I figure that clothing serves a functional purpose as well as a decorative one. Though I have been attracted to people who appeared to own only one pair of pants, I generally prefer a look that involves a little bit more range than that.
Accessories: not big on them.
Cologne: no.
Other hygiene: shower as needed.
Facial hair: grow it out, trim so it doesn't get explosive. I do not want to see food in your beard. That is just gross.
Yup.