Most Helpful Girl
It depends on what kind of relationship you are having. I know some really hot hot guys who have married the ugliest, and I mean seriously ugly girls.
The key however is to appear neat, pleasant, & completely obvious that you are good at taking care of yourself. Also being confident as in you feel comfortable in your own skin.
Other than that, if you know your strengths, (which you MUST, because dating or not, it is the first & most important thing in life you should focus on before even thinking about breathing, water, & food) you might have an idea of what he is attracted to in you. Most of the times it's your strengths, but there's also a good chance with guys that it is actually what you hate most about yourself. (From what I've seen, unlike girls, guys do not act on cliches when it comes to personal matters, tastes, or opinions). So bottom line, find out what he likes in you, & take care on it.
P. s. some guys are face guys, some are boobies, some bootie, some overall figure, however some are all about mentality, character/personality, or even culture. (A good way to understand such things is to get close enough with his family)