Beauty is objective up to a point. What that means is that a woman can be a 10 to one man and an 8 to another, but she is unlikely to be less than a 5. So if we're not counting fetishes or very specific preferences, I'd say a woman can generally vary around 3 points from one man to another. IME, a 'traditionally' attractive woman (swimsuit model style) will be between 7-9.
A woman's number is never definite though. A woman who's an 8+ does a LOT to maintain that, and most women can certainly change their efforts to increase several points. Not everybody can be an 8 or more, but most women can tone up and make efforts with their hair/makeup.
Are men visual? Yes. Being good looking does not guarantee happiness, but the general rule is that your looks attract a man, your personality will make him stay.
In terms of what is attractive, I consider that obvious. Clear, glowing skin, symmetrical features, full lips, big eyes, small nose. A slim body with some curves. Long, full and shiny hair. Looks which signalize fertility and are feminine.
Men will try to get a woman who's as beautiful as they can, or at least what they think they deserve. They will choose a woman who's 1 or 2 points lower if she has a much better personality, but they won't go way lower than their potential.
So, what are women to do? Become as attractive as you can be, have a positive and lovely personality, aim for the right guys.