How can I approach a girl if she shows interest?


So like i remember a girl smiling and staring at me but i was too awkward to say anything and i got scared and looked/walked away. I don’t wanna make the same mistake again.

If a girl happens to show some sort of interest, how do we approach them, I want to smile but my smile is bad and when i smile, it just twitches. I know i gotta walk up to them but i feel like a npc if i do that and I don't know what to say after “hi” What do i even say? Please someone with experience tell me

How can I approach a girl if she shows interest?
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