What's going on?

There's this one girl I recently really like. I'm really confused about what she may think of me. Back a couple years I liked her and I can recall hearing from my friend who supposedly heard from her boyfriend, who is now her ex and one of my friends, that she thought I was creepy. I have a huge staring problem where I could literally be staring at somebody for an hour and not even realize it, without even liking them. However, she's now in my choir class and she's been giving me all these shy smiles. I've been led to believe that it's either the "hey, I like you" smile or the "hey, you're a freak" smile. I'm worried that it's the latter but I've heard from girls that there is no freak smile and she might actually like me. I talked to her today and she seemed really excited that I had been talking to her and I could also tell she might have been a tad shy or nervous. However, according to a different people, one being my sister and the other being a girl friend of mine who I think likes me and hates her, she always acts that way and actually likes a different guy. Even if she does like me, I'm not even entirely sure what to do about it. I want to ask her to homecoming which is in a month. I typically know what girls want and I have a lot of experience talking to all my girl friends about this but I've never actually had a girlfriend, even though I help all my friends get girlfriends. So what does she think of me? How long should I really know her before I ask her out?