If beauty is in the eye of the beholder -- aren't some things, people in this case, ugly? What really determines this?

Symmetry is often a fair indicator of genetic health. Not surprising that symmetrical features are generally found to be attractive across different cultures.

Some interesting research on this topic.

One’s own personal taste.

Sometimes I will not be too attracted to a man’s appearance, but will enjoy his sense of humor, or intelligence, or something about his personality, and then I will start to appreciate his appearance more. Looks aren’t everything. They’re just a part of the total package.

I should add that conversely, a man can be very handsome but if he has the personality of an asshole or a wet dishrag, then his handsomeness goes right out the window.

I was going to mention the symmetry research too.

I think part of our idea of beauty is learned.

For me it starts with the hourglass figure and is cemented by personality.

I agree @JLeslie. I think the base of it, the symmetry, is instinctive. Things after that, like tattoos, piercing, clothing, those are learned preferences.

And for women it’s the opposite @ARE_you_kidding_me. We notice his personality first, his smile, the look in his eyes and quickly judge if is he’s rapey or creepy, and if he’s not, then we start to notice physical details. I can’t speak for other women, but just because a man is physcially attractive it doesn’t make me want to jump right in bed with him. The “I really care” thing has to be there first, and that can take weeks or month to cultivate.
As far as what I find physically attractive, I start with the arms, especially the forearms. And they nicely muscular from working hard? Not necessarily bulky, from working out, but strong? And his upper arms and shoulders are next.

One of my sons by another mother is a small, very slight young man. He is married to a very large, very fat women. He is wild about her! She would in no way be considered attractive across the board, but he’s crazy in love with her. That’s a good example.

Oh it can go that way for guys too. Usually though it’s the opposite. Same thing about attitude, an attractive woman with a shit personality will get ugly real quick.