If you want to be attractive, wear some good looking clothes, like the Elegant Prince or Princess outfit, depending on your gender, being thin is a good help, using the right tattoo set and hairstyle works as well, and high morality is always a must. Or if you wish to be ugly, you can choose to gain weight, lower your morality, and wear hideous clothing. There are also some weapons which can increase your attractiveness, once upgraded.
(Actually, High morality isn't a must. My friend is pure Evil, but Has High attractivness levels)