Personalized contact can do a LOT, and make girls feel like you want her individually to join. If you're still considered to be in pre-rush, then you are probably okay to individually contact/meet with girls (find out the rules!) and get to know them on an individual basis. If a girl feels like she's not being treated generically, or mass-invited to things, she will probably feel more special--you really want
her, and maybe she'll tell her friends about the awesome club where they really went out of their way to get to know her.
Best of luck to you!