How to approach a girl that is almost always with friends?

Ok, so there is this girl that I like. She is younger than me (Both in High school) and she is sort of popular. What do I do to prevent ridicule and what is an easy way to approach her. Keep in mind she is always with a couple friends in hallways which makes it difficult to talk to her for the first time. What is a way to prevent her from being with a group or how do I separate her from that group cleverly?