How do i get closer to this girl im interested in?

i know this girl for a little while and we get along well, i dont see her that oftern but every now and then we run into eachother and i'd like it to be more than that, i get a good vibe from her and i think if i could actually hang out with her and get to know her well it could go places, i dont have her number, sn, n were not friends on facebook i think it would be creepy to get her number from someone and text her out of the blue, same with friending her on facebook, any suggestions/advice?