Well, I'm not an expert with this kind of stuff, but my best friend sure is! I will now share with you everything he taught me. Do you like this girl or are you just having trouble talking to girls?
Either way, you just simply have to greet her. Start off simple like "hi" or "what's up?". If you like this girl, you just have to be relaxed(I admit I failed at this a couple times
). Don't keep living with "what if" like "What if she's gonna think I'm weird?". You just gotta let it go and treat her normally like you treat everyone else and be yourself. Don't try to act cool or anything like that because even though she likes it, the more you keep talking, you're gonna start to lose that acting cool and you'll slowly turn back to yourself and she's gonna find out you've been faking it the whole time. And one of the most important things I've learned when talking to a girl you like is to never go too fast. Just take it slow make sure she gets comfortable with you. But remember, bro, these are just guiding words for you. These things alone won't get you anywhere. It all depends on how you handle your next conversation with this girl. All of this is just to prepare you for it.
Best of luck!!!