Is it normal to ask a friend out?

SO a girl sits next to me in English class...complete stranger to me. She has been giving me some "signals" if you want to call it that and usually when I get those "signals" I approach with no problem. I know what to do. But, with girls I actually like it's different. I feel and see her staring at me many times. She jokes around with me as I've been friends with her for years. She messes with me by tapping me and giggling. She once took my essay paper and book without asking, so I see how really comfortable she is with messing with me. I know there are many girls out there who like to flirt for just nothing. But, is it normal to want to make something of it, possibly? Should I do something, and if so what is it that should I do?