Again, this seems like a no-brainer, but Styles loves a girl that he can have a good conversation or banter with. That would explain that rumor that Styles wanted to start dating only British women, because only they can appreciate his dry and sarcastic sense of humor. (That rumor is completely untrue, by the way.) Being able to talk to the 1D singer for hours on end will not only endear you to him, but it's also just good practice for any relationship ever. Why hang out with someone you can't talk to?
You Must Be Yourself
That seems like a bizarre thing to put on a list of things Styles is looking for in a girlfriend, but at the end of the day, all Styles really wants is for girls to be themselves around him. In his own (possible) words, Swift wasn't his type, but he liked her anyway. You don't have to actively try, or change yourself, to get Styles to like you. Just do you, and good things might follow.