A proper way to ask a girl out?

So I been meaning to ask this girl out for awhile, but now I don't see her face to face anymore. The only way I can get a hold of her would be through Facebook. I really want to start hanging out with her, but wouldn't trying to ask someone out through text just be a little shallow, as opposed to doing it in front of her? If I had to do the FB approach, what would be a decent response/buildup in order for me to ask her out? I don't see her on campus anymore, because this semester we have differen't schedules... :/