It all depends on who you're talking to of course.
For me, it's very important for the woman to be smaller than I am. (probably prideful reasons, but you want honesty)
Symmetry is important in the entire body.
Cleanliness is paramount. What you wear, how prone you are to acne, how you have your hair etc.
There are all kinds of different shapes for breasts, asses and midsections that are attractive to different types of men. I like girls that have an obvious curve from the bottom of the ribcage to the hips without being skinny. A healthy weight that will make sure your hips bones and ribs aren't clearly defined.
Some smaller things are fingernails that extend a little bit past the tip of the finger, how you fix your hair, how often you make the effort to look good.
Try to look natural, little to no makeup, it works well. Stay active and healthy and you'll attract anyone. Have you tried asking people who know what you look like? Eventually you'll get a response that you know is the truth, even though some people might say "of course!" out of love. Don't go looking for a "no" of course.
For myself, I've come to form an opinion that attractiveness isn't something that is measured on a linear scale, like from 1 to 10. It's an idea that is more abstract, more fluid like water. The only way you can measure water is if you try to contain it. If you pour water on a table you can't measure it, but everyone will develop a different perception of how much water is there. And if you freeze it or heat it up, the perceptions as to how much water is there become distorted. The relation to attraction is that in a situation or society individuals try to create a general measuring method to contain or judge what is attractive, like judging people from 1 to 10. Or developing gallons or liters to measure water. Which is better, metric or english measurement? Depends on the environment you're interacting in and how you feel. It's like picking out clothes. Trying to determine "what looks better" doesn't fulfill it's potential until you imagine what you're going to be doing that day and how you feel. Now, say I get dressed and I'm gonna go to the gym (for example) and there's two gym's. One gym is full of bodybuilders and the other is full of people who happen to be elderly. My perception of "if I look good" and the other people's perceptions around me change as the environment that I am interacting with changes. The elderly people don't care what I look like and the bodybuilders will think I'm not bulked up enough or whatever. And when I encounter the elderly people I would probably care less what I look like and around the bodybuilder I might judge why I like the way I look better or why I might need to exercise more. To me, it's a more complex idea than "this person is a 6, she's a 9, he's a 4-and-a-half (lol, throwing it out there)".
whatever you do, stay skinny and work on your muscles from time to time. other than that isn't much you can do. just be confident and develop a great personality.
it's been shown that people who are 9s and 10s or whatever, end up suffering psychologically when they grow older. they no longer have their good looks and lack skills/interests in other areas.
i liked bonpatron's answer but like even if you got 5/8 'bad things' doesn't mean you're ugly.. it means you need to take care of yourself. Nice clothing meaning wear clean clothing. Solid colours in general are safe. Stop biting your nails, it takes 40 days to build a habit and 40 days to get out of one. Its okay if you wear make-up, just don't wear too much (thats probably why you have irritated skin causing it to be acne prone). Use cleansers and wash your face and hands often. Don't put too much sh*t on your face like make up and stuff every day. use cleansers, creams or make up that doesn't make your skin oily because this causes break outs. If you're seriously worried about frizzy hair, you can easily tie it up or get a hair straightener. Ugliness has a lot to do about self-esteem and self-negligence. Some people accept that they're ugly and let themselves go. Always love yourself, be confident and take care of your body.