What Should I Do about this Girl?

I was at a party for one of my good friends on Saturday night and while I was there, this girl walked in and sat at the table all of my friends were at. She was sharing a seat with someone across the table, so I figured this friend and her were dating. I talked with her a little, mostly small talk if anything, and when we left I made sure to say goodbye to her and shake her hand. I hadn't caught her name either, so I asked her that as well. Anyway, since that night, I can't get her out of my mind. It turns out, according to someone I talked to, that she isn't dating the kid she was sitting with and is seemingly single. I knew she had an Instagram, so I made one and followed her after making sure it looked like is been on Instagram for more than a night. However, she hasn't followed me back yet. I know it's only been a few hours, but what should I do if she doesn't follow back? Should I send her a direct message? How can I talk to her and get her to like me? Other things? Thanks for your help!