Flirting with a girl?

There's this girl I like at my school , I don't know her and I wanna go talk her and get to know her , I wanna flirt with her to show that I mean to be more than friends but the problem is I can't seem to catch her alone and I don't wanna flirt with her infront of her friends . What do you suggest? Alone or with friends or get her to leave her friends